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81 lines
2.9 KiB
Text
81 lines
2.9 KiB
Text
drop table if exists t1;
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SET SQL_SAFE_UPDATES=1,SQL_SELECT_LIMIT=4, SQL_MAX_JOIN_SIZE=9;
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create table t1 (a int auto_increment primary key, b char(20));
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insert into t1 values(1,"test");
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SELECT SQL_BUFFER_RESULT * from t1;
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a b
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1 test
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update t1 set b="a" where a=1;
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delete from t1 where a=1;
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insert into t1 values(1,"test"),(2,"test2");
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SELECT SQL_BUFFER_RESULT * from t1;
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a b
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1 test
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2 test2
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update t1 set b="a" where a=1;
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select 1 from t1,t1 as t2,t1 as t3;
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1
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1
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1
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1
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1
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update t1 set b="a";
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You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
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update t1 set b="a" where b="test";
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You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
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delete from t1;
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You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
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delete from t1 where b="test";
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You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
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delete from t1 where a+0=1;
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You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
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select 1 from t1,t1 as t2,t1 as t3,t1 as t4,t1 as t5;
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The SELECT would examine more rows than MAX_JOIN_SIZE. Check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is ok
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update t1 set b="a" limit 1;
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update t1 set b="a" where b="b" limit 2;
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delete from t1 where b="test" limit 1;
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delete from t1 where a+0=1 limit 2;
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alter table t1 add key b (b);
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SET MAX_JOIN_SIZE=2;
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SELECT @@MAX_JOIN_SIZE, @@SQL_BIG_SELECTS;
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@@max_join_size @@sql_big_selects
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2 0
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insert into t1 values (null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a");
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SELECT * from t1 order by a;
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The SELECT would examine more rows than MAX_JOIN_SIZE. Check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is ok
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SET SQL_BIG_SELECTS=1;
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SELECT * from t1 order by a;
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a b
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2 test2
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3 a
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4 a
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5 a
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SET MAX_JOIN_SIZE=2;
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SELECT * from t1;
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The SELECT would examine more rows than MAX_JOIN_SIZE. Check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is ok
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SET MAX_JOIN_SIZE=DEFAULT;
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SELECT * from t1;
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a b
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2 test2
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3 a
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4 a
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5 a
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SELECT @@MAX_SEEKS_FOR_KEY;
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@@max_seeks_for_key
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4294967295
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analyze table t1;
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Table Op Msg_type Msg_text
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test.t1 analyze status OK
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insert into t1 values (null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a");
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explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
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table type possible_keys key key_len ref rows Extra
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t1 ALL b NULL NULL NULL 21
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t2 ALL b NULL NULL NULL 16 Using where
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set MAX_SEEKS_FOR_KEY=1;
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explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
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table type possible_keys key key_len ref rows Extra
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t1 ALL b NULL NULL NULL 21
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t2 ref b b 21 t1.b 6 Using where
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SET MAX_SEEKS_FOR_KEY=DEFAULT;
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drop table t1;
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SET SQL_SAFE_UPDATES=0,SQL_SELECT_LIMIT=DEFAULT, SQL_MAX_JOIN_SIZE=DEFAULT;
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