# Boolean Expression
__*Boolean expression*__
+ Constant name:**TRUE** and**FALSE** in any case 
  + The result of**TRUE** is**1**
  + The result of**FALSE** is**0**
+ **BOOLEAN** data types are actually defined as `TINYINT (1)` 
+ For example: 
  + `select 1=true, 1=TRUE, true;` 
```
tidb> SELECT 1=true, 1=TRUE, true;
+--------+--------+------+
| 1=true | 1=TRUE | TRUE |
+--------+--------+------+
|      1 |      1 |    1 |
+--------+--------+------+
1 row in set (0.00 sec)
```

------------------------------------------------------------
```
tidb> create table test.bgl (id boolean);
Query OK, 0 rows affected (0.10 sec)

tidb> desc test.bgl;
+-------+------------+------+------+---------+-------+
| Field | Type       | Null | Key  | Default | Extra |
+-------+------------+------+------+---------+-------+
| id    | tinyint(1) | YES  |      | NULL    |       |
+-------+------------+------+------+---------+-------+
1 row in set (0.00 sec)

tidb> insert into test.bgl values (true), (false), (123);
Query OK, 3 rows affected (0.02 sec)
Records: 3 Duplicates: 0 Warnings: 0

tidb> select * from test.bgl;
+------+
| id   |
+------+
| 1    |
| 0    |
| 123  |
+------+
3 rows in set (0.00 sec)
```