Hi guys,
look at the following test case:
mysql> create table temp1( id int)ENGINE=innodb;
Query OK, 0 rows affected (0.18 sec)
mysql> create table temp2( tid varchar(10))ENGINE=innodb;
Query OK, 0 rows affected (0.07 sec)
mysql> insert into temp1 values(1);
Query OK, 1 row affected (0.07 sec)
mysql> insert into temp1 values(2);
Query OK, 1 row affected (0.05 sec)
mysql> insert into temp1 values(3);
Query OK, 1 row affected (0.04 sec)
mysql> insert into temp1 values(4);
Query OK, 1 row affected (0.04 sec)
mysql> insert into temp2 values('2,3,4');
Query OK, 1 row affected (0.05 sec)
mysql> commit;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from temp1;
+------+
| id |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
+------+
4 rows in set (0.01 sec)
mysql> select * from temp2;
+-------+
| tid |
+-------+
| 2,3,4 |
+-------+
1 row in set (0.00 sec)
mysql> select * from temp1 where id in (select tid from temp2);
+------+
| id |
+------+
| 2 |
+------+
1 row in set (0.00 sec)
The problem:
Why there is result for the last SELECT statement???
How does mysql compare id with tid ?? they are different type and have
different format value.
Thanks a lot!!!
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