# Bool

`Bool` represents the two logical values `true` and `false`. `BOOLEAN` is an alias.

## Syntax

```text
Bool
BOOLEAN
```

## Accepted values

A Boolean conversion accepts `true`, `false`, numeric `0` and `1`, and their equivalent flag text. Other numeric values are rejected rather than treated as true.

Boolean columns can be used directly in `WHERE`, `CASE` and conditional aggregate expressions. SQL `NULL` remains a missing value; declare `NOT NULL` when a column must always have a flag.

## Examples

### Converting flags

```sql
SELECT CAST('true' AS Bool), CAST(0 AS Bool), CAST(1 AS BOOLEAN)
FORMAT csv;
```

```text
true,false,true
```

### Filtering by a Boolean column

```sql
CREATE TABLE tasks(id UInt32, completed Bool NOT NULL);
INSERT INTO tasks VALUES (1, true), (2, false), (3, true);
```

```sql
SELECT id
FROM tasks
WHERE completed
ORDER BY id
FORMAT csv;
```

```text
1
3
```

See [logical functions](https://coordinatordb.com/docs/reference/functions/regular-functions/logical-functions) and [NULL functions](https://coordinatordb.com/docs/reference/functions/regular-functions/functions-for-nulls) for Boolean expressions with missing values.