mirror of
https://github.com/MariaDB/server.git
synced 2025-01-18 04:53:01 +01:00
264 lines
8.9 KiB
Text
264 lines
8.9 KiB
Text
SET @@session.storage_engine = 'MyISAM';
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create table t1 (a int,
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b int as (-a),
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c int as (-a) persistent,
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index (c));
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insert into t1 (a) values (2), (1), (1), (3), (NULL);
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create table t2 like t1;
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insert into t2 (a) values (1);
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create table t3 (a int primary key,
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b int as (-a),
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c int as (-a) persistent unique);
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insert into t3 (a) values (2),(1),(3);
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# select_type=SIMPLE, type=system
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select * from t2;
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a b c
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1 -1 -1
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explain select * from t2;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 system NULL NULL NULL NULL 1
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select * from t2 where c=-1;
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a b c
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1 -1 -1
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explain select * from t2 where c=-1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 system c NULL NULL NULL 1
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# select_type=SIMPLE, type=ALL
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select * from t1 where b=-1;
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a b c
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1 -1 -1
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1 -1 -1
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explain select * from t1 where b=-1;
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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 5 Using where
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# select_type=SIMPLE, type=const
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select * from t3 where a=1;
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a b c
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1 -1 -1
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explain select * from t3 where a=1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 const PRIMARY PRIMARY 4 const 1
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# select_type=SIMPLE, type=range
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select * from t3 where c>=-1;
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a b c
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1 -1 -1
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explain select * from t3 where c>=-1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 range c c 5 NULL 2 Using where
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# select_type=SIMPLE, type=ref
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select * from t1,t3 where t1.c=t3.c and t3.c=-1;
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a b c a b c
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1 -1 -1 1 -1 -1
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1 -1 -1 1 -1 -1
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explain select * from t1,t3 where t1.c=t3.c and t3.c=-1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 const c c 5 const 1
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1 SIMPLE t1 ref c c 5 const 2 Using where
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# select_type=PRIMARY, type=index,ALL
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select * from t1 where b in (select c from t3);
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a b c
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2 -2 -2
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1 -1 -1
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1 -1 -1
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3 -3 -3
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explain select * from t1 where b in (select c from t3);
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1 ALL NULL NULL NULL NULL 5 Using where
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2 DEPENDENT SUBQUERY t3 index_subquery c c 5 func 2 Using index; Using where
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# select_type=PRIMARY, type=range,ref
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select * from t1 where c in (select c from t3 where c between -2 and -1);
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a b c
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2 -2 -2
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1 -1 -1
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1 -1 -1
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explain select * from t1 where c in (select c from t3 where c between -2 and -1);
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1 ALL NULL NULL NULL NULL 5 Using where
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2 DEPENDENT SUBQUERY t3 index_subquery c c 5 func 2 Using index; Using where
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# select_type=UNION, type=system
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# select_type=UNION RESULT, type=<union1,2>
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select * from t1 union select * from t2;
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a b c
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2 -2 -2
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1 -1 -1
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3 -3 -3
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NULL NULL NULL
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explain select * from t1 union select * from t2;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1 ALL NULL NULL NULL NULL 5
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2 UNION t2 system NULL NULL NULL NULL 1
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NULL UNION RESULT <union1,2> ALL NULL NULL NULL NULL NULL
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# select_type=DERIVED, type=system
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select * from (select a,b,c from t1) as t11;
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a b c
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2 -2 -2
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1 -1 -1
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1 -1 -1
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3 -3 -3
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NULL NULL NULL
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explain select * from (select a,b,c from t1) as t11;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY <derived2> ALL NULL NULL NULL NULL 5
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2 DERIVED t1 ALL NULL NULL NULL NULL 5
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###
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### Using aggregate functions with/without DISTINCT
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###
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# SELECT COUNT(*) FROM tbl_name
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select count(*) from t1;
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count(*)
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5
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explain select count(*) from t1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
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# SELECT COUNT(DISTINCT <non-vcol>) FROM tbl_name
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select count(distinct a) from t1;
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count(distinct a)
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3
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explain select count(distinct a) from t1;
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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 5
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# SELECT COUNT(DISTINCT <non-stored vcol>) FROM tbl_name
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select count(distinct b) from t1;
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count(distinct b)
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3
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explain select count(distinct b) from t1;
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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 5
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# SELECT COUNT(DISTINCT <stored vcol>) FROM tbl_name
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select count(distinct c) from t1;
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count(distinct c)
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3
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explain select count(distinct c) from t1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 index NULL c 5 NULL 5 Using index
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###
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### filesort & range-based utils
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###
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# SELECT * FROM tbl_name WHERE <vcol expr>
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select * from t3 where c >= -2;
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a b c
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2 -2 -2
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1 -1 -1
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explain select * from t3 where c >= -2;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 range c c 5 NULL 2 Using where
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# SELECT * FROM tbl_name WHERE <non-vcol expr>
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select * from t3 where a between 1 and 2;
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a b c
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1 -1 -1
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2 -2 -2
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explain select * from t3 where a between 1 and 2;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 range PRIMARY PRIMARY 4 NULL 1 Using where
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# SELECT * FROM tbl_name WHERE <non-indexed vcol expr>
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select * from t3 where b between -2 and -1;
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a b c
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2 -2 -2
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1 -1 -1
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explain select * from t3 where b between -2 and -1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 ALL NULL NULL NULL NULL 3 Using where
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# SELECT * FROM tbl_name WHERE <indexed vcol expr>
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select * from t3 where c between -2 and -1;
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a b c
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2 -2 -2
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1 -1 -1
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explain select * from t3 where c between -2 and -1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 range c c 5 NULL 1 Using where
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# SELECT * FROM tbl_name WHERE <non-vcol expr> ORDER BY <indexed vcol>
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select * from t3 where a between 1 and 2 order by c;
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a b c
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2 -2 -2
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1 -1 -1
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explain select * from t3 where a between 1 and 2 order by c;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 range PRIMARY PRIMARY 4 NULL 1 Using where; Using filesort
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# SELECT * FROM tbl_name WHERE <non-indexed vcol expr> ORDER BY <non-vcol>
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select * from t3 where b between -2 and -1 order by a;
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a b c
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1 -1 -1
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2 -2 -2
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explain select * from t3 where b between -2 and -1 order by a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 ALL NULL NULL NULL NULL 3 Using where; Using filesort
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# SELECT * FROM tbl_name WHERE <indexed vcol expr> ORDER BY <non-vcol>
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select * from t3 where c between -2 and -1 order by a;
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a b c
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1 -1 -1
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2 -2 -2
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explain select * from t3 where c between -2 and -1 order by a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 range c c 5 NULL 1 Using where; Using filesort
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# SELECT * FROM tbl_name WHERE <non-indexed vcol expr> ORDER BY <non-indexed vcol>
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select * from t3 where b between -2 and -1 order by b;
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a b c
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2 -2 -2
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1 -1 -1
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explain select * from t3 where b between -2 and -1 order by b;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 ALL NULL NULL NULL NULL 3 Using where; Using filesort
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# SELECT * FROM tbl_name WHERE <indexed vcol expr> ORDER BY <non-indexed vcol>
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select * from t3 where c between -2 and -1 order by b;
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a b c
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2 -2 -2
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1 -1 -1
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explain select * from t3 where c between -2 and -1 order by b;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 range c c 5 NULL 1 Using where; Using filesort
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# SELECT * FROM tbl_name WHERE <non-indexed vcol expr> ORDER BY <indexed vcol>
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select * from t3 where b between -2 and -1 order by c;
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a b c
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2 -2 -2
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1 -1 -1
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explain select * from t3 where b between -2 and -1 order by c;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 ALL NULL NULL NULL NULL 3 Using where; Using filesort
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# SELECT * FROM tbl_name WHERE <indexed vcol expr> ORDER BY <indexed vcol>
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select * from t3 where c between -2 and -1 order by c;
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a b c
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2 -2 -2
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1 -1 -1
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explain select * from t3 where c between -2 and -1 order by c;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t3 range c c 5 NULL 1 Using where
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# SELECT sum(<non-indexed vcol>) FROM tbl_name GROUP BY <non-indexed vcol>
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select sum(b) from t1 group by b;
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sum(b)
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NULL
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-3
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-2
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-2
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explain select sum(b) from t1 group by b;
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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 5 Using temporary; Using filesort
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# SELECT sum(<indexed vcol>) FROM tbl_name GROUP BY <indexed vcol>
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select sum(c) from t1 group by c;
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sum(c)
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NULL
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-3
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-2
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-2
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explain select sum(c) from t1 group by c;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 index NULL c 5 NULL 5 Using index
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# SELECT sum(<non-indexed vcol>) FROM tbl_name GROUP BY <indexed vcol>
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select sum(b) from t1 group by c;
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sum(b)
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NULL
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-3
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-2
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-2
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explain select sum(b) from t1 group by c;
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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 5 Using temporary; Using filesort
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# SELECT sum(<indexed vcol>) FROM tbl_name GROUP BY <non-indexed vcol>
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select sum(c) from t1 group by b;
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sum(c)
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NULL
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-3
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-2
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-2
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explain select sum(c) from t1 group by b;
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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 5 Using temporary; Using filesort
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