# OData logical operators in Azure Cognitive Search - `and`

, `or`

, `not`

OData filter expressions in Azure Cognitive Search are Boolean expressions that evaluate to `true`

or `false`

. You can write a complex filter by writing a series of simpler filters and composing them using the logical operators from Boolean algebra:

`and`

: A binary operator that evaluates to`true`

if both its left and right sub-expressions evaluate to`true`

.`or`

: A binary operator that evaluates to`true`

if either one of its left or right sub-expressions evaluates to`true`

.`not`

: A unary operator that evaluates to`true`

if its sub-expression evaluates to`false`

, and vice-versa.

These, together with the collection operators `any`

and `all`

, allow you to construct filters that can express very complex search criteria.

## Syntax

The following EBNF (Extended Backus-Naur Form) defines the grammar of an OData expression that uses the logical operators.

```
logical_expression ::=
boolean_expression ('and' | 'or') boolean_expression
| 'not' boolean_expression
```

An interactive syntax diagram is also available:

Note

See OData expression syntax reference for Azure Cognitive Search for the complete EBNF.

There are two forms of logical expressions: binary (`and`

/`or`

), where there are two sub-expressions, and unary (`not`

), where there is only one. The sub-expressions can be Boolean expressions of any kind:

- Fields or range variables of type
`Edm.Boolean`

- Functions that return values of type
`Edm.Boolean`

, such as`geo.intersects`

or`search.ismatch`

- Comparison expressions, such as
`rating gt 4`

- Collection expressions, such as
`Rooms/any(room: room/Type eq 'Deluxe Room')`

- The Boolean literals
`true`

or`false`

. - Other logical expressions constructed using
`and`

,`or`

, and`not`

.

Important

There are some situations where not all kinds of sub-expression can be used with `and`

/`or`

, particularly inside lambda expressions. See OData collection operators in Azure Cognitive Search for details.

### Logical operators and `null`

Most Boolean expressions such as functions and comparisons cannot produce `null`

values, and the logical operators cannot be applied to the `null`

literal directly (for example, `x and null`

is not allowed). However, Boolean fields can be `null`

, so you need to be aware of how the `and`

, `or`

, and `not`

operators behave in the presence of null. This is summarized in the following table, where `b`

is a field of type `Edm.Boolean`

:

Expression | Result when `b` is `null` |
---|---|

`b` |
`false` |

`not b` |
`true` |

`b eq true` |
`false` |

`b eq false` |
`false` |

`b eq null` |
`true` |

`b ne true` |
`true` |

`b ne false` |
`true` |

`b ne null` |
`false` |

`b and true` |
`false` |

`b and false` |
`false` |

`b or true` |
`true` |

`b or false` |
`false` |

When a Boolean field `b`

appears by itself in a filter expression, it behaves as if it had been written `b eq true`

, so if `b`

is `null`

, the expression evaluates to `false`

. Similarly, `not b`

behaves like `not (b eq true)`

, so it evaluates to `true`

. In this way, `null`

fields behave the same as `false`

. This is consistent with how they behave when combined with other expressions using `and`

and `or`

, as shown in the table above. Despite this, a direct comparison to `false`

(`b eq false`

) will still evaluate to `false`

. In other words, `null`

is not equal to `false`

, even though it behaves like it in Boolean expressions.

## Examples

Match documents where the `rating`

field is between 3 and 5, inclusive:

```
rating ge 3 and rating le 5
```

Match documents where all elements of the `ratings`

field are less than 3 or greater than 5:

```
ratings/all(r: r lt 3 or r gt 5)
```

Match documents where the `location`

field is within the given polygon, and the document does not contain the term "public".

```
geo.intersects(location, geography'POLYGON((-122.031577 47.578581, -122.031577 47.678581, -122.131577 47.678581, -122.031577 47.578581))') and not search.ismatch('public')
```

Match documents for hotels in Vancouver, Canada where there is a deluxe room with a base rate less than 160:

```
Address/City eq 'Vancouver' and Address/Country eq 'Canada' and Rooms/any(room: room/Type eq 'Deluxe Room' and room/BaseRate lt 160)
```