$and¶
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$and
¶ Syntax:
{ $and: [ { <expression1> }, { <expression2> } , ... , { <expressionN> } ] }
$and
performs a logicalAND
operation on an array of two or more expressions (e.g.<expression1>
,<expression2>
, etc.) and selects the documents that satisfy all the expressions in the array. The$and
operator uses short-circuit evaluation. If the first expression (e.g.<expression1>
) evaluates tofalse
, MongoDB will not evaluate the remaining expressions.Note
MongoDB provides an implicit
AND
operation when specifying a comma separated list of expressions. Using an explicitAND
with the$and
operator is necessary when the same field or operator has to be specified in multiple expressions.
Examples¶
AND
Queries With Multiple Expressions Specifying the Same Field¶
Consider the following example:
db.inventory.find( { $and: [ { price: { $ne: 1.99 } }, { price: { $exists: true } } ] } )
This query will select all documents in the inventory
collection where:
- the
price
field value is not equal to1.99
and - the
price
field exists.
This query can be also be constructed with an implicit AND
operation by combining the operator expressions for the price
field. For example, this query can be written as:
db.inventory.find( { price: { $ne: 1.99, $exists: true } } )
AND
Queries With Multiple Expressions Specifying the Same Operator¶
Consider the following example:
db.inventory.find( {
$and : [
{ $or : [ { price : 0.99 }, { price : 1.99 } ] },
{ $or : [ { sale : true }, { qty : { $lt : 20 } } ] }
]
} )
This query will select all documents where:
- the
price
field value equals0.99
or1.99
, and - the
sale
field value is equal totrue
or theqty
field value is less than20
.
This query cannot be constructed using an implicit AND
operation,
because it uses the $or
operator more than once.