Subqueries with IN
语法描述
子查询可以与 IN 操作符一起使用，作为“表达式 IN (子查询)”，查询某个范围内的数据。子查询应该返回带有一行或多行的单个列，以形成 IN 操作使用的值列表。
对多记录、单列子查询使用 IN 子句。子查询返回 IN 或 NOT IN 引入的结果后，外部查询使用它们返回最终结果。
-
如果子查询结果中有匹配的行，则结果为
TRUE。 -
如果子查询结果为
NULL，则返回结果为false。 -
如果子查询结果中没有匹配的行，结果也是
FALSE。 -
如果子查询结果中所有的值都为
NULL，则返回结果为false。
语法结构
> SELECT ... FROM table_name WHERE column_name IN (subquery)
示例
create table t1(val varchar(10));
insert into t1 values ('aaa'), ('bbb'),('eee'),('mmm'),('ppp');
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%');
+----------+
| count(*) |
+----------+
| 0 |
+----------+
1 row in set (0.01 sec)
create table t1 (id int not null, text varchar(20) not null default '', primary key (id));
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');
mysql> select * from t1 where id not in (select id from t1 where id < 8);
+------+--------+
| id | text |
+------+--------+
| 8 | text8 |
| 9 | text9 |
| 10 | text10 |
| 11 | text11 |
| 12 | text12 |
+------+--------+
5 rows in set (0.00 sec)
CREATE TABLE t1 (a int);
CREATE TABLE t2 (a int, b int);
CREATE TABLE t3 (b int NOT NULL);
INSERT INTO t1 VALUES (1), (2), (3), (4);
INSERT INTO t2 VALUES (1,10), (3,30);
mysql> select * from t1 where t1.a in (SELECT t1.a FROM t1 LEFT JOIN t2 ON t2.a=t1.a);
+------+
| a |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
+------+
4 rows in set (0.01 sec)
mysql> SELECT * FROM t2 LEFT JOIN t3 ON t2.b=t3.b WHERE t3.b IS NOT NULL OR t2.a > 10;
Empty set (0.01 sec)
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);
+------+
| a |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
+------+
4 rows in set (0.00 sec)
create table t1 (a int);
create table t2 (a int, b int);
create table t3 (a int);
create table t4 (a int not null, b int not null);
create table t5 (a int);
create table t6 (a int, b int);
insert into t1 values (2);
insert into t2 values (1,7),(2,7);
insert into t4 values (4,8),(3,8),(5,9);
insert into t5 values (null);
insert into t3 values (6),(7),(3);
insert into t6 values (10,7),(null,7);
mysql> select a,b from t6 where (a,b) in ( select a,b from t4 where a>3);
Empty set (0.02 sec)