# **IS NULL**

## **Grammar Description**

The `IS NULL` operator is used to determine whether the column's value is empty. If the value is empty, it is `NULL`, then return `true`, otherwise return `false`. It can be used in `SELECT`, `INSERT`, `UPDATE` or `DELETE` statements.

## **Grammar Structure**

```text
> expression IS NULL
```

## **Example**

```text
mysql> SELECT 1 IS NULL, 0 IS NULL, NULL IS NULL;
+------------------------------------------------------------------------------------------------------------------------------
| 1 is null | 0 is null | null is null |
+------------------------------------------------------------------------------------------------------------------------------
| false | false | true |
+------------------------------------------------------------------------------------------------------------------------------
1 row in set (0.01 sec)
```

```text
create table t1 (a boolean,b bool);
insert into t1 values (0,1),(true,false),(true,1),(0,false),(NULL,NULL);

mysql> select * from t1;
+--------+--------+
| a | b |
+--------+--------+
| false | true |
| true | false |
| true | true |
| false | false |
| NULL | NULL |
+--------+--------+
mysql> select * from t1 where a IS NULL;
+------+------+
| a | b |
+------+------+
| NULL | NULL |
+------+------+
1 row in set (0.01 sec)
```