#  `IN` 和 `EXISTS` 

__*IN*__
__*EXISTS*__

+ IN 和 EXISTS 之间的区别  

```10
tidb> SELECT * FROM test.t1;
+------+
| id   |
+------+
| NULL |
+------+
1 row in set (0.00 sec)
tidb> SELECT * FROM test.t1 WHERE id ~!@IN@!~ (SELECT id FROM test.t1);
Empty set (0.00 sec)
tidb> SELECT * FROM test.t1 WHERE ~!@EXISTS@!~ (SELECT id FROM test.t1);
+------+
| id   |
+------+
| NULL |
+------+
1 row in set (0.01 sec)
```
----------------------------------------------------------
IN 对数据的值感兴趣, EXISTS 对记录的存在感兴趣而不是具体的数值。