$or¶

$or¶

New in version 1.6.

Changed in version 2.0: You may nest $or operations; however, these expressions are not as efficiently optimized as top-level.

Syntax: { $or: [ { <expression1> }, { <expression2> }, ... , { <expressionN> } ] }

The $or operator performs a logical OR operation on an array of two or more <expressions> and selects the documents that satisfy at least one of the <expressions>.

Consider the following query:

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db.inventory.find( { price:1.99, $or: [ { qty: { $lt: 20 } }, { sale: true } ] } )

This query will select all documents in the inventory collection where:

the price field value equals 1.99 and
either the qty field value is less than 20 or the sale field value is true.

Consider the following example which uses the $or operator to select fields from embedded documents:

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db.inventory.update( { $or: [ { price:10.99 }, { "carrier.state": "NY"} ] }, { $set: { sale: true } } )

This update() operation will set the value of the sale field in the documents in the inventory collection where:

the price field value equals 10.99 or
the carrier embedded document contains a field state whose value equals NY.

When using $or with <expressions> that are equality checks for the value of the same field, choose the $in operator over the $or operator.

Consider the query to select all documents in the inventory collection where:

either price field value equals 1.99 or the sale field value equals true, and
either qty field value equals 20 or qty field value equals 50,

The most effective query would be:

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db.inventory.find ( { $or: [ { price: 1.99 }, { sale: true } ], qty: { $in: [20, 50] } } )

Consider the following behaviors when using the $or operator:

When using indexes with $or queries, remember that each clause of an $or query can use its own index. Consider the following query:
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```
db.inventory.find ( { $or: [ { price: 1.99 }, { sale: true } ] } )
```
For this query, you would create one index on price ( db.inventory.ensureIndex( { price: 1 } ) ) and another index on sale ( db.inventory.ensureIndex( { sale: 1 } ) ) rather than a compound index.
Also, when using the $or operator with the sort() method in a query, the query will not use the indexes on the $or fields. Consider the following query which adds a sort() method to the above query:
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```
db.inventory.find ( { $or: [ { price: 1.99 }, { sale: true } ] } ).sort({item:1})
```
This modified query will not use the index on price nor the index on sale.
You cannot use the $or operator with 2d geospatial queries.