$lt (aggregation)
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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 Expression Operators.
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 }