$lt (expression operator)

Definition

$lt

Compares two values and returns:

true when the first value is less than the second value.
false when the first value is greater than or equivalent to the second value.

The $lt compares both value and type, using the specified BSON comparison order for values of different types.

$lt has the following syntax:

{ $lt: [ <expression1>, <expression2> ] }

For more information on expressions, see Expressions.

Example

Consider an inventory collection with the following documents:

db.inventory.insertMany( [   { _id : 1, item : "abc1", description: "product 1", qty: 300 },   { _id : 2, item : "abc2", description: "product 2", qty: 200 },   { _id : 3, item : "xyz1", description: "product 3", qty: 250 },   { _id : 4, item : "VWZ1", description: "product 4", qty: 300 },   { _id : 5, item : "VWZ2", description: "product 5", qty: 180 }] )

The following operation uses the $lt operator to determine if qty is less than 250:

db.inventory.aggregate(   [     {       $project:          {            item: 1,            qty: 1,            qtyLt250: { $lt: [ "$qty", 250 ] },            _id: 0          }     }   ])

The operation returns the following results:

{ item: "abc1", qty: 300, qtyLt250: false }{ item: "abc2", qty: 200, qtyLt250: true }{ item: "xyz1", qty: 250, qtyLt250: false }{ item: "VWZ1", qty: 300, qtyLt250: false }{ item: "VWZ2", qty: 180, qtyLt250: true }

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