Subqueries with IN

Description

A subquery can be used with the IN operator as “expression IN (subquery)”. The subquery should return a single column with one or more rows to form a list of values to be used by the IN operation.

Use the IN clause for multiple-record, single-column subqueries. After the subquery returns results introduced by IN or NOT IN, the outer query uses them to return the final result.

  • If any row in the sub-query result matches, the answer is true.
  • If the subquery result is empty, the answer is false.
  • If no row in the sub-query result matches, the answer is also false.
  • If all of the values in the sub-query result are null, the answer is false.

Syntax

1. > SELECT ... FROM table_name WHERE column_name IN (subquery)

Examples

1. create table t1(val varchar(10));
2. insert into t1 values ('aaa'), ('bbb'),('eee'),('mmm'),('ppp');

4. mysql> select count(*) from t1 as w1 where w1.val in (select w2.val from t1 as w2 where w2.val like 'm%') and w1.val in (select w3.val from t1 as w3 where w3.val like 'e%');
5. +----------+
6. | count(*) |
7. +----------+
8. |        0 |
9. +----------+
10. 1 row in set (0.01 sec)

1. create table t1 (id int not null, text varchar(20) not null default '', primary key (id));
2. insert into t1 (id, text) values (1, 'text1'), (2, 'text2'), (3, 'text3'), (4, 'text4'), (5, 'text5'), (6, 'text6'), (7, 'text7'), (8, 'text8'), (9, 'text9'), (10, 'text10'), (11, 'text11'), (12, 'text12');

4. mysql> select * from t1 where id not in (select id from t1 where id < 8);
5. +------+--------+
6. | id   | text   |
7. +------+--------+
8. |    8 | text8  |
9. |    9 | text9  |
10. |   10 | text10 |
11. |   11 | text11 |
12. |   12 | text12 |
13. +------+--------+
14. 5 rows in set (0.00 sec)

1. CREATE TABLE t1 (a int);
2. CREATE TABLE t2 (a int, b int);
3. CREATE TABLE t3 (b int NOT NULL);
4. INSERT INTO t1 VALUES (1), (2), (3), (4);
5. INSERT INTO t2 VALUES (1,10), (3,30);

7. mysql> select * from t1 where t1.a in (SELECT t1.a FROM t1 LEFT JOIN t2 ON t2.a=t1.a);
8. +------+
9. | a    |
10. +------+
11. |    1 |
12. |    2 |
13. |    3 |
14. |    4 |
15. +------+
16. 4 rows in set (0.01 sec)

18. mysql> SELECT * FROM t2 LEFT JOIN t3 ON t2.b=t3.b WHERE t3.b IS NOT NULL OR t2.a > 10;
19. Empty set (0.01 sec)
20. mysql> SELECT * FROM t1 WHERE t1.a NOT IN (SELECT a FROM t2 LEFT JOIN t3 ON t2.b=t3.b WHERE t3.b IS NOT NULL OR t2.a > 10);
21. +------+
22. | a    |
23. +------+
24. |    1 |
25. |    2 |
26. |    3 |
27. |    4 |
28. +------+
29. 4 rows in set (0.00 sec)

1. create table t1 (a int);
2. create table t2 (a int, b int);
3. create table t3 (a int);
4. create table t4 (a int not null, b int not null);
5. create table t5 (a int);
6. create table t6 (a int, b int);
7. insert into t1 values (2);
8. insert into t2 values (1,7),(2,7);
9. insert into t4 values (4,8),(3,8),(5,9);
10. insert into t5 values (null);
11. insert into t3 values (6),(7),(3);
12. insert into t6 values (10,7),(null,7);

14. mysql> select a,b from t6 where (a,b) in ( select a,b from t4 where a>3);
15. Empty set (0.02 sec)