## Syntax
```mermaid
%%{init: {
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'themeVariables': {
'fontSize': '11px',
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flowchart LR
Start((START)) --> IS_BOOLEAN[IS_BOOLEAN]:::quoted
IS_BOOLEAN --> End((END))
```
## Purpose
The `IS_BOOLEAN` SQL function evaluates to `true` when a value is representing a valid boolean. A valid boolean can be cast to a `boolean` value using [[TO_BOOLEAN]]. The [[TO_BOOLEAN]] SQL function also defines the castable boolean values.
Parameters:
- Input (`ANY`): value to test whether a cast to `boolean` is possible.
Returns: true when the text can be cast to a `boolean`, false otherwise.
## Examples
The following example determines whether `'true'` can be cast to a `boolean`:
```sql
select is_boolean('true')
----------------
true
```
The following example determines whether `'tr'` can be cast to a `boolean`:
```sql
select is_boolean('tr')
----------------
false
```