mirror of
https://github.com/MariaDB/server.git
synced 2025-01-16 20:12:31 +01:00
986 lines
24 KiB
Text
986 lines
24 KiB
Text
CREATE OR REPLACE TABLE t1(a int, b int) engine=aria;
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CREATE OR REPLACE TABLE t2(a int, b int) engine=aria;
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insert into t1 values (1,10),(2,20),(3,30);
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insert into t2 values (2,21),(3,31),(4,41);
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#
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# Simple selects
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#
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select a,b,rownum() from t1;
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a b rownum()
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1 10 1
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2 20 2
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3 30 3
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select a,b,rownum() from t1 where rownum() < 2;
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a b rownum()
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1 10 1
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select a,b from t1 where rownum() <= 2;
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a b
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1 10
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2 20
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select a,b from t1 where rownum() > 2;
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a b
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#
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# Subqueries
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#
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select t1.a,rownum(),t3.a,t3.t2_rownum from t1, (select t2.a,rownum() as t2_rownum from t2 where rownum() <=2) t3;
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a rownum() a t2_rownum
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1 1 2 1
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1 2 3 2
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2 3 2 1
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2 4 3 2
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3 5 2 1
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3 6 3 2
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select t1.a, (select t2.b from t2 where t1.a=t2.a and rownum() <= 1) 'b' from t1;
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a b
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1 NULL
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2 21
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3 31
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select t1.a, t3.a from t1, (select * from t2 where rownum() <= 2) t3;
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a a
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1 2
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1 3
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2 2
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2 3
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3 2
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3 3
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select * from (select tt.*,rownum() as id from (select * from t1) tt) t3 where id>2;
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a b id
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3 30 3
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#
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# Joins
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#
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select t1.a,t1.b,t2.a,t2.b,rownum() from t1,t2 where rownum() <= 4;
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a b a b rownum()
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1 10 2 21 1
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2 20 2 21 2
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3 30 2 21 3
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1 10 3 31 4
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select *,rownum() from t1,t2 where t1.a=t2.a and rownum()<=2;
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a b a b rownum()
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2 20 2 21 1
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3 30 3 31 2
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select * from t1 left join t2 on (t2.a=t1.a and rownum()=0);
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a b a b
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1 10 NULL NULL
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2 20 NULL NULL
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3 30 NULL NULL
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select * from t1 left join t2 on (t2.a=t1.a and rownum()>1);
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a b a b
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1 10 NULL NULL
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2 20 NULL NULL
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3 30 NULL NULL
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select * from t1 left join t2 on (t2.a=t1.a and rownum()<1);
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a b a b
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1 10 NULL NULL
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2 20 NULL NULL
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3 30 NULL NULL
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select * from t1 left join t2 on (t2.a=t1.a and rownum()=1);
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a b a b
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2 20 2 21
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1 10 NULL NULL
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3 30 NULL NULL
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select * from t1 left join t2 on (t2.a=t1.a and rownum()>=1);
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a b a b
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2 20 2 21
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3 30 3 31
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1 10 NULL NULL
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#
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# Union
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#
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select * from t1 where rownum() <=2 union select * from t2 where rownum()<= 1;
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a b
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1 10
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2 20
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2 21
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#
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# Order by
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#
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select * from t1 where rownum() <= 2 order by a desc;
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a b
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2 20
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1 10
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explain select * from t1 where rownum() <= 2 order by a desc;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 3 Using where; Using filesort
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select t1.a,t1.b,rownum() from t1 where rownum() <= 2 order by a desc;
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a b rownum()
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2 20 2
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1 10 1
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explain select t1.a,t1.b,rownum() from t1 where rownum() <= 2 order by a desc;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 3 Using where; Using temporary; Using filesort
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select *,rownum() from t1,t2;
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a b a b rownum()
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1 10 2 21 1
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2 20 2 21 2
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3 30 2 21 3
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1 10 3 31 4
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2 20 3 31 5
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3 30 3 31 6
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1 10 4 41 7
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2 20 4 41 8
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3 30 4 41 9
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select *,rownum() from t1,t2 order by t2.a desc, t1.a desc;
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a b a b rownum()
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3 30 4 41 9
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2 20 4 41 8
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1 10 4 41 7
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3 30 3 31 6
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2 20 3 31 5
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1 10 3 31 4
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3 30 2 21 3
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2 20 2 21 2
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1 10 2 21 1
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select * from (select * from t1 order by a desc) as t where rownum() <= 2;
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a b
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3 30
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2 20
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select * from t1,t2 where t1.a=t2.a and rownum()<=2 order by t1.a,t2.a;
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a b a b
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2 20 2 21
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3 30 3 31
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#
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# Having
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#
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select t1.a, sum(t1.b), rownum() as 'r' from t1 group by t1.a having r <= 2;
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a sum(t1.b) r
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1 10 1
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2 20 2
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select * from t1 having rownum() <= 2;
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a b
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1 10
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2 20
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select t1.a, sum(t1.b), rownum() from t1 group by t1.a;
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a sum(t1.b) rownum()
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1 10 1
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2 20 2
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3 30 3
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select t1.a, sum(t1.b), rownum() as 'r' from t1 group by t1.a having r <= 2;
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a sum(t1.b) r
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1 10 1
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2 20 2
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select t1.a, sum(t1.b), rownum() as 'r' from t1 group by t1.a having rownum() <= 2;
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a sum(t1.b) r
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1 10 1
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2 20 2
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select t1.a, sum(t1.b), rownum() as 'r' from t1 group by t1.a having r <= 2 order by a desc;
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a sum(t1.b) r
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2 20 2
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1 10 1
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select t1.a, sum(t1.b), rownum() as 'r' from t1 group by t1.a having rownum() <= 2 order by a desc;
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a sum(t1.b) r
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2 20 2
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1 10 1
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#
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# Sum functions
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#
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select max(rownum()),min(rownum()) from t1;
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max(rownum()) min(rownum())
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3 1
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select sum(rownum()),avg(rownum()) from t1;
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sum(rownum()) avg(rownum())
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6 2.0000
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#
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# Group by
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#
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select t1.a,sum(t1.b) from t1 where rownum() < 2 group by t1.a;
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a sum(t1.b)
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1 10
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select t1.a,sum(t2.b) from t1 JOIN t2 ON (t1.a=t2.a) where rownum() <= 2 group by t1.a;
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a sum(t2.b)
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2 21
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3 31
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select * from (select t1.a,sum(t2.b) from t1 JOIN t2 ON (t1.a=t2.a) group by t1.a) as t where rownum() <= 1;
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a sum(t2.b)
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2 21
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select t1.a,sum(rownum()),count(*) from t1 where rownum() <= 2 group by t1.a;
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a sum(rownum()) count(*)
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1 1 1
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2 2 1
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select * from (select t1.a,sum(t1.b) from t1 group by t1.a) as t3 where rownum() < 2;
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a sum(t1.b)
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1 10
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create table t3 (a int) engine=myisam;
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insert into t3 values (3),(5),(5),(3);
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select a, max(rownum()) from t3 group by a;
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a max(rownum())
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3 4
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5 3
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drop table t3;
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CREATE TABLE t3 (
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a int(11) DEFAULT NULL,
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b varchar(1024) DEFAULT NULL
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);
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insert into t3 select mod(seq*3,20)+1, repeat(char(33+mod(seq,90)),mod(seq,10)*100) from seq_1_to_23;
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SELECT sq.a,length(sq.f) FROM (SELECT a, GROUP_CONCAT(b,b) AS f FROM t3 GROUP BY a ORDER BY a desc) as sq WHERE ROWNUM() <= 10;
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a length(sq.f)
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20 600
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19 1200
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18 1800
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17 400
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16 1000
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15 1600
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14 200
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13 800
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12 1400
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11 0
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drop table t3;
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#
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# Prepared statements
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#
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PREPARE stmt1 from "select a,b,rownum() from t1 where rownum() <= 2";
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execute stmt1;
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a b rownum()
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1 10 1
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2 20 2
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execute stmt1;
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a b rownum()
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1 10 1
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2 20 2
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deallocate prepare stmt1;
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#
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# Views
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#
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create view v1 as select t1.a,rownum() from t1;
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select * from v1;
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a rownum()
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1 1
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2 2
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3 3
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select t1.a,v1.* from t1,v1 where t1.a=v1.a;
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a a rownum()
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1 1 1
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2 2 2
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3 3 3
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drop view v1;
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CREATE TABLE t3 (a INT);
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INSERT INTO t3 VALUES (1),(2),(3);
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CREATE VIEW v1 AS SELECT a FROM t3 WHERE ROWNUM() <= 2;
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SELECT * FROM v1;
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a
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1
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2
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drop view v1;
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drop table t3;
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#
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# Reserved words
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#
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create table t4 (a int, rownum int);
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insert into t4 (a,rownum) values (1,2);
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select t4.a,t4.rownum from t4;
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a rownum
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1 2
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drop table t4;
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#
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# Test Oracle mode
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#
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set SQL_MODE=ORACLE;
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select t1.a,rownum from t1 where rownum<=2;
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a rownum
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1 1
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2 2
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select t1.a,rownum() from t1 where rownum()<=2;
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a rownum()
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1 1
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2 2
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create table t4 (a int, rownum int);
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ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'rownum int)' at line 1
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DECLARE
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CURSOR c_cursor
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IS select a,b,rownum from t1 where rownum <= 2;
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v_a t1.a%TYPE;
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v_b t1.b%TYPE;
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v_rn t1.a%TYPE;
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BEGIN
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OPEN c_cursor;
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FETCH c_cursor INTO v_a, v_b, v_rn;
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WHILE c_cursor%FOUND LOOP
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SELECT concat(v_a,'--',v_b,'--',v_rn);
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FETCH c_cursor INTO v_a, v_b, v_rn;
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END LOOP;
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CLOSE c_cursor;
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END;|
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concat(v_a,'--',v_b,'--',v_rn)
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1--10--1
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concat(v_a,'--',v_b,'--',v_rn)
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2--20--2
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select a, rownum from t1 group by a, rownum having rownum < 3;
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a rownum
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1 1
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2 2
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select a, rownum as r from t1 group by a, rownum having r < 3;
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a r
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1 1
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2 2
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select a, rownum from t1 group by a, rownum having "rownum" < 3;
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a rownum
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1 1
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2 2
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select a, rownum from t1 group by a, rownum having rownum < 3 order by a desc;
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a rownum
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2 2
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1 1
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select a, rownum as r from t1 group by a, rownum having r < 3 order by a desc;
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a r
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2 2
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1 1
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select a, rownum from t1 group by a, rownum having "rownum" < 3 order by a desc;
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a rownum
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2 2
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1 1
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set SQL_MODE=DEFAULT;
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# Cleanup
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drop table t1,t2;
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#
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# INSERT
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#
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create table t1 (a int not null primary key, b int);
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insert into t1 values (1,rownum()),(2,rownum()),(3,rownum());
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select * from t1;
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a b
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1 1
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2 2
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3 3
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drop table t1;
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#
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# INSERT DELAYED
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#
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create table t1 (a int not null primary key, b int);
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insert delayed into t1 values (1,rownum()),(2,rownum()),(3,rownum());
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select * from t1;
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a b
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1 1
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2 2
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3 3
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drop table t1;
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#
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# INSERT IGNORED
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#
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create table t1 (a int not null primary key, b int);
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insert ignore into t1 values (1,rownum()),(2,rownum()),(2,rownum()),(3,rownum());
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Warnings:
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Warning 1062 Duplicate entry '2' for key 'PRIMARY'
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select * from t1;
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a b
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1 1
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2 2
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3 4
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delete from t1;
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insert ignore into t1 select * from (values (1,rownum()),(2,rownum()),(2,rownum()),(3,rownum())) t;
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Warnings:
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Warning 1062 Duplicate entry '2' for key 'PRIMARY'
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select * from t1;
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a b
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1 1
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2 2
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3 4
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drop table t1;
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#
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# INSERT ... RETURNING
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#
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create or replace table t1 (a int);
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insert into t1 values (1),(2) returning a, rownum();
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a rownum()
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1 1
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2 2
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drop table t1;
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#
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# UPDATE
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#
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create table t1 (a int not null primary key, b int);
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insert into t1 values (1,1),(2,2),(3,3);
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update t1 set b=0;
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update t1 set b=rownum()+1;
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select * from t1;
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a b
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1 2
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2 3
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3 4
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update t1 set b=0;
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update t1 set b=rownum() where a < 10 and rownum() < 2;
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select * from t1;
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a b
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1 1
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2 0
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3 0
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drop table t1;
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create table t1 (a int);
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insert into t1 values (10),(20),(30);
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update t1 set a = rownum();
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select * from t1;
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a
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1
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2
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3
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update t1 set a = rownum();
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select * from t1;
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a
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1
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2
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3
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drop table t1;
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#
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# DELETE
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#
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create table t1 (a int not null primary key, b int);
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insert into t1 values (1,1),(2,0),(3,0);
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delete from t1 where a < 10 and rownum() < 2;
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select * from t1;
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a b
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2 0
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3 0
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drop table t1;
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#
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# MULTI-TABLE-DELETE
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#
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create table t1 (a int not null primary key);
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insert into t1 values (1),(2),(3);
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create table t2 (a int not null primary key);
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insert into t2 values (1),(2),(3);
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delete t1,t2 from t1,t2 where t1.a=t2.a and rownum() <= 2;
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select * from t1;
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a
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3
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select * from t2;
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a
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3
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drop table t1,t2;
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#
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# MULTI-TABLE-UPDATE
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CREATE TABLE t1 (ID INT);
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CREATE TABLE t2 (ID INT,
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s1 TEXT, s2 TEXT, s3 VARCHAR(10), s4 TEXT, s5 VARCHAR(10));
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INSERT INTO t1 VALUES (1),(2);
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INSERT INTO t2 VALUES (1,'test', 'test', 'test', 'test', 'test'),
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(2,'test', 'test', 'test', 'test', 'test');
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SELECT * FROM t1 LEFT JOIN t2 USING(ID);
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ID s1 s2 s3 s4 s5
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1 test test test test test
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2 test test test test test
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UPDATE t1 LEFT JOIN t2 USING(ID) SET s1 = 'changed';
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select * from t2;
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ID s1 s2 s3 s4 s5
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1 changed test test test test
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2 changed test test test test
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update t2 set s1="";
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UPDATE t1 LEFT JOIN t2 USING(ID) SET s1 = 'changed' where rownum() <=1;
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select * from t2;
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ID s1 s2 s3 s4 s5
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1 changed test test test test
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2 test test test test
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drop table t1,t2;
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#
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# LOAD DATA
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#
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create table t1 (a int, b int, c int);
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load data infile '../../std_data/loaddata7.dat' into table t1 fields terminated by ',' lines terminated by "\r\n" (a,b) set c=rownum();
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select * from t1;
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a b c
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2 2 1
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3 3 2
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4 4 3
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5 5 4
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6 6 5
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drop table t1;
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#
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# LIMIT OPTIMIZATION
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#
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create table t1 (a int);
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insert into t1 select seq from seq_1_to_100;
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flush status;
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select * from t1 where rownum() <= 3;
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a
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1
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2
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3
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show status like "Rows_read";
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Variable_name Value
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Rows_read 3
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flush status;
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select * from t1 where rownum() <= 4 and rownum() <= 3;
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a
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1
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2
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3
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show status like "Rows_read";
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Variable_name Value
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Rows_read 3
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flush status;
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select * from t1 where rownum() < 4 and a > 10;
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a
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11
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12
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|
13
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 13
|
|
flush status;
|
|
select * from t1 where 3 >= rownum();
|
|
a
|
|
1
|
|
2
|
|
3
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 3
|
|
flush status;
|
|
select * from t1 where 4 > rownum() and a > 20;
|
|
a
|
|
21
|
|
22
|
|
23
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 23
|
|
flush status;
|
|
select * from t1 where rownum() = 1 and a > 10;
|
|
a
|
|
11
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 11
|
|
flush status;
|
|
select * from t1 where a > 30 && 1 = rownum();
|
|
a
|
|
31
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 31
|
|
flush status;
|
|
# No limit optimization
|
|
select * from t1 where rownum() > 10;
|
|
a
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 100
|
|
flush status;
|
|
select * from t1 where 10 < rownum();
|
|
a
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 100
|
|
flush status;
|
|
select * from t1 where rownum() >= 10;
|
|
a
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 100
|
|
flush status;
|
|
select * from t1 where 10 < rownum();
|
|
a
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 100
|
|
flush status;
|
|
select * from t1 where 10 <= rownum();
|
|
a
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 100
|
|
flush status;
|
|
select * from t1 where 2 = rownum();
|
|
a
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 100
|
|
flush status;
|
|
select * from t1 where rownum() = 2;
|
|
a
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 100
|
|
flush status;
|
|
select * from t1 where rownum() <= 0;
|
|
a
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 100
|
|
flush status;
|
|
select *,rownum() from t1 where rownum() < 10 limit 4, 4;
|
|
a rownum()
|
|
5 5
|
|
6 6
|
|
7 7
|
|
8 8
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 8
|
|
flush status;
|
|
select * from t1 where rownum() < 10 order by a;
|
|
a
|
|
1
|
|
2
|
|
3
|
|
4
|
|
5
|
|
6
|
|
7
|
|
8
|
|
9
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 100
|
|
flush status;
|
|
# rownum and limit
|
|
select * from t1 where rownum() < 4 limit 10;
|
|
a
|
|
1
|
|
2
|
|
3
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 3
|
|
flush status;
|
|
select * from t1 where rownum() < 10 limit 4;
|
|
a
|
|
1
|
|
2
|
|
3
|
|
4
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 4
|
|
drop table t1;
|
|
#
|
|
# Rownum examples from Woqutech
|
|
#
|
|
set SQL_MODE=ORACLE;
|
|
create table t1 (c1 int ,c2 varchar(20)) engine=myisam;
|
|
insert into t1 values (1, 'aaa'),(2, 'bbb'),(3, 'ccc'),(4, 'ddd'),(5, 'eee');
|
|
update t1 set c2 = 'xxx' where rownum = 2;
|
|
select * from t1 where c2='xxx';
|
|
c1 c2
|
|
update t1 set c2 = 'xxx' where rownum < 3;
|
|
select * from t1 where c2='xxx';
|
|
c1 c2
|
|
1 xxx
|
|
2 xxx
|
|
delete from t1 where rownum = 2;
|
|
select count(*) from t1;
|
|
count(*)
|
|
5
|
|
delete from t1 where rownum < 3;
|
|
select count(*) from t1;
|
|
count(*)
|
|
3
|
|
delete from t1 where c1=rownum ;
|
|
select count(*) from t1;
|
|
count(*)
|
|
3
|
|
delete from t1 where c1=rownum+2 ;
|
|
select count(*) from t1;
|
|
count(*)
|
|
0
|
|
set SQL_MODE=DEFAULT;
|
|
drop table t1;
|
|
#
|
|
# Rownum() used in not supported places (returns 0 or gives an error)
|
|
#
|
|
set @a=rownum();
|
|
select @a;
|
|
@a
|
|
0
|
|
create or replace table t (a int, b int as (rownum()) virtual);
|
|
ERROR HY000: Function or expression 'rownum()' cannot be used in the GENERATED ALWAYS AS clause of `b`
|
|
create table t1 (a int);
|
|
insert into t1 values (3),(1),(5),(8),(4);
|
|
handler t1 open;
|
|
handler t1 read next where rownum() < 1;
|
|
ERROR HY000: Function or expression 'rownum()' cannot be used in the WHERE clause of `HANDLER`
|
|
handler t1 close;
|
|
drop table t1;
|
|
create table t1 (a int not null primary key, b int);
|
|
insert into t1 values (1,1),(2,2),(3,3);
|
|
create function f() returns int return rownum();
|
|
select a, rownum(), f() from t1;
|
|
a rownum() f()
|
|
1 1 0
|
|
2 2 0
|
|
3 3 0
|
|
drop function f;
|
|
drop table t1;
|
|
create or replace table t1 (a int, r int);
|
|
create trigger tr before update on t1 for each row set NEW.r = rownum();
|
|
insert into t1 (a) values (1),(2);
|
|
select * from t1;
|
|
a r
|
|
1 NULL
|
|
2 NULL
|
|
update t1 set a=a+10;
|
|
select * from t1;
|
|
a r
|
|
11 0
|
|
12 0
|
|
drop trigger tr;
|
|
drop table t1;
|
|
#
|
|
# LIMIT optimisation
|
|
#
|
|
create table t1 (a int);
|
|
insert into t1 values (1),(2),(3),(4),(5);
|
|
flush status;
|
|
select * from (select a from t1 where a < 1000) as tt where rownum() <= 2;
|
|
a
|
|
1
|
|
2
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 2
|
|
explain extended select * from (select a from t1 where a < 1000) as tt where rownum() <= 2;
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00 Using where
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 limit 2) `tt` where rownum() <= 2 limit 2
|
|
prepare stmt from "select * from (select a from t1 where a < 1000) as tt where rownum() <= 2";
|
|
flush status;
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 2
|
|
flush status;
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 2
|
|
deallocate prepare stmt;
|
|
flush status;
|
|
select * from (select a from t1 where a < 1000 group by a) as tt where rownum() <= 2;
|
|
a
|
|
1
|
|
2
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 5
|
|
explain extended select * from (select a from t1 where a < 1000 group by a) as tt where rownum() <= 2;
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00 Using where
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where; Using temporary; Using filesort
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 group by `test`.`t1`.`a` limit 2) `tt` where rownum() <= 2 limit 2
|
|
prepare stmt from "select * from (select a from t1 where a < 1000 group by a) as tt where rownum() <= 2";
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
deallocate prepare stmt;
|
|
flush status;
|
|
select * from (select a from t1 where a < 1000 group by a order by 1) as tt where rownum() <= 2;
|
|
a
|
|
1
|
|
2
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 5
|
|
explain extended select * from (select a from t1 where a < 1000 group by a order by 1) as tt where rownum() <= 2;
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00 Using where
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where; Using temporary; Using filesort
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 group by `test`.`t1`.`a` order by 1 limit 2) `tt` where rownum() <= 2 limit 2
|
|
prepare stmt from "select * from (select a from t1 where a < 1000 group by a order by 1) as tt where rownum() <= 2";
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
deallocate prepare stmt;
|
|
flush status;
|
|
select * from (select a from t1 where a < 1000 union select 10) as tt where rownum() <= 2;
|
|
a
|
|
1
|
|
2
|
|
show status like "Rows_read";
|
|
Variable_name Value
|
|
Rows_read 5
|
|
explain extended select * from (select a from t1 where a < 1000 union select 10) as tt where rownum() <= 2;
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00 Using where
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where
|
|
3 UNION NULL NULL NULL NULL NULL NULL NULL NULL No tables used
|
|
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL NULL
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 union /* select#3 */ select 10 AS `10` limit 2) `tt` where rownum() <= 2 limit 2
|
|
prepare stmt from "select * from (select a from t1 where a < 1000 union select 10) as tt where rownum() <= 2";
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
deallocate prepare stmt;
|
|
# Other limit
|
|
select * from (select a from t1 where a < 1000 group by a order by 1 limit 1) as tt where rownum() <= 2;
|
|
a
|
|
1
|
|
explain extended select * from (select a from t1 where a < 1000 group by a order by 1 limit 1) as tt where rownum() <= 2;
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00 Using where
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where; Using temporary; Using filesort
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 group by `test`.`t1`.`a` order by 1 limit 1) `tt` where rownum() <= 2 limit 2
|
|
prepare stmt from "select * from (select a from t1 where a < 1000 group by a order by 1 limit 1) as tt where rownum() <= 2";
|
|
execute stmt;
|
|
a
|
|
1
|
|
execute stmt;
|
|
a
|
|
1
|
|
deallocate prepare stmt;
|
|
# Other limit less
|
|
select * from (select a from t1 where a < 1000 group by a order by 1 limit 10) as tt where rownum() <= 2;
|
|
a
|
|
1
|
|
2
|
|
explain extended select * from (select a from t1 where a < 1000 group by a order by 1 limit 10) as tt where rownum() <= 2;
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00 Using where
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where; Using temporary; Using filesort
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 group by `test`.`t1`.`a` order by 1 limit 2) `tt` where rownum() <= 2 limit 2
|
|
prepare stmt from "select * from (select a from t1 where a < 1000 group by a order by 1 limit 10) as tt where rownum() <= 2";
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
deallocate prepare stmt;
|
|
select * from (select a from t1 where a < 1000 union select 10 limit 1) as tt where rownum() <= 2;
|
|
a
|
|
1
|
|
explain extended select * from (select a from t1 where a < 1000 union select 10 limit 1) as tt where rownum() <= 2;
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 5 100.00 Using where
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where
|
|
3 UNION NULL NULL NULL NULL NULL NULL NULL NULL No tables used
|
|
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL NULL
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 union /* select#3 */ select 10 AS `10` limit 1) `tt` where rownum() <= 2 limit 2
|
|
prepare stmt from "select * from (select a from t1 where a < 1000 union select 10 limit 1) as tt where rownum() <= 2";
|
|
execute stmt;
|
|
a
|
|
1
|
|
execute stmt;
|
|
a
|
|
1
|
|
deallocate prepare stmt;
|
|
# < rownum
|
|
select * from (select a from t1 where a < 1000) as tt where rownum() < 2;
|
|
a
|
|
1
|
|
explain extended select * from (select a from t1 where a < 1000) as tt where rownum() < 2;
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00 Using where
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 limit 1) `tt` where rownum() < 2 limit 1
|
|
prepare stmt from "select * from (select a from t1 where a < 1000) as tt where rownum() < 2";
|
|
execute stmt;
|
|
a
|
|
1
|
|
execute stmt;
|
|
a
|
|
1
|
|
deallocate prepare stmt;
|
|
# Simple expression
|
|
select * from (select a from t1 where a < 1000) as tt where rownum() <= 1+1;
|
|
a
|
|
1
|
|
2
|
|
explain extended select * from (select a from t1 where a < 1000) as tt where rownum() <= 1+1;
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00 Using where
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 limit 2) `tt` where rownum() <= <cache>(1 + 1) limit 2
|
|
prepare stmt from "select * from (select a from t1 where a < 1000) as tt where rownum() <= 1+1";
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
deallocate prepare stmt;
|
|
# Simple expression reversed
|
|
select * from (select a from t1 where a < 1000) as tt where 1+1 >= rownum();
|
|
a
|
|
1
|
|
2
|
|
explain extended select * from (select a from t1 where a < 1000) as tt where 1+1 >= rownum();
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00 Using where
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 limit 2) `tt` where <cache>(1 + 1) >= rownum() limit 2
|
|
prepare stmt from "select * from (select a from t1 where a < 1000) as tt where 1+1 >= rownum()";
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
deallocate prepare stmt;
|
|
# expensive (no opt)
|
|
select * from (select a from t1 where a < 1000) as tt where (select max(a) from t1) >= rownum();
|
|
a
|
|
1
|
|
2
|
|
3
|
|
4
|
|
5
|
|
explain extended select * from (select a from t1 where a < 1000) as tt where (select max(a) from t1) >= rownum();
|
|
id select_type table type possible_keys key key_len ref rows filtered Extra
|
|
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 5 100.00 Using where
|
|
3 SUBQUERY t1 ALL NULL NULL NULL NULL 5 100.00
|
|
2 DERIVED t1 ALL NULL NULL NULL NULL 5 100.00 Using where
|
|
Warnings:
|
|
Note 1003 /* select#1 */ select `tt`.`a` AS `a` from (/* select#2 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` < 1000 limit 5) `tt` where (/* select#3 */ select max(`test`.`t1`.`a`) from `test`.`t1`) >= rownum() limit 5
|
|
prepare stmt from "select * from (select a from t1 where a < 1000) as tt where (select max(a) from t1) >= rownum()";
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
3
|
|
4
|
|
5
|
|
execute stmt;
|
|
a
|
|
1
|
|
2
|
|
3
|
|
4
|
|
5
|
|
deallocate prepare stmt;
|
|
drop table t1;
|
|
#
|
|
# Table value constructors
|
|
#
|
|
values ("first row"),("next row is 3"),(rownum()),("next row is 5"),(rownum());
|
|
first row
|
|
first row
|
|
next row is 3
|
|
3
|
|
next row is 5
|
|
5
|