SQL
Logical Operators
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The following logical operators are available: `AND`, `OR` and `NOT`. SQL uses a three-valuad logic system with `true`, `false` and `NULL`. Note that logical operators involving `NULL` do not always evaluate to `NULL`. For example, `NULL AND false` will evaluate to `false`, and `NULL OR true` will evaluate to `true`. Below are the complete truth tables.  
#### Binary Operators: `AND` and `OR` {#docs:sql:expressions:logical_operators::binary-operators-and-and-or}  
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| `a` | `b` | `a AND b` | `a OR b` |
|:---|:---|:---|:---|
| `true` | `true` | `true` | `true` |
| `true` | `false` | `false` | `true` |
| `true` | `NULL` | `NULL` | `true` |
| `false` | `false` | `false` | `false` |
| `false` | `NULL` | `false` | `NULL` |
| `NULL` | `NULL` | `NULL` | `NULL`|  
#### Unary Operator: `NOT` {#docs:sql:expressions:logical_operators::unary-operator-not}  
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| `a` | `NOT a` |
|:---|:---|
| `true` | `false` |
| `false` | `true` |
| `NULL` | `NULL` |  
The operators `AND` and `OR` are commutative, that is, you can switch the left and right operand without affecting the result.