$min
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Definition
$minThe
$minupdates the value of the field to a specified value if the specified value is less than the current value of the field. The$minoperator can compare values of different types, using the BSON comparison order.{ $min: { <field1>: <value1>, ... } } To specify a
<field>in an embedded document or in an array, use dot notation.
Behavior
Starting in MongoDB 5.0, update operators process document fields with string-based names in lexicographic order. Fields with numeric names are processed in numeric order. See Update Operators Behavior for details.
If the field does not exist, the $min operator sets the
field to the specified value.
For comparisons between values of different types, such as a number and
a null, $min uses the BSON comparison order.
Starting in MongoDB 5.0, mongod no longer raises an
error when you use an update operator like $min
with an empty operand expression ( { } ). An empty update results
in no changes and no oplog entry is created (meaning that the
operation is a no-op).
Examples
Use $min to Compare Numbers
Create the scores collection:
db.scores.insertOne( { _id: 1, highScore: 800, lowScore: 200 } )
The lowScore for the document currently has the value
200. The following operation uses $min to compare
200 to the specified value 150 and updates the value of
lowScore to 150 since 150 is less than 200:
db.scores.updateOne( { _id: 1 }, { $min: { lowScore: 150 } } )
The scores collection now contains the following modified document:
{ _id: 1, highScore: 800, lowScore: 150 }
The next operation has no effect since the current value of the
field lowScore, i.e 150, is less than 250:
db.scores.updateOne( { _id: 1 }, { $min: { lowScore: 250 } } )
The document remains unchanged in the scores collection:
{ _id: 1, highScore: 800, lowScore: 150 }
Use $min to Compare Dates
Create the tags collection:
db.tags.insertOne( { _id: 1, desc: "crafts", dateEntered: ISODate("2013-10-01T05:00:00Z"), dateExpired: ISODate("2013-10-01T16:38:16Z") } )
The following operation compares the current value of the
dateEntered field, i.e. ISODate("2013-10-01T05:00:00Z"),
with the specified date new Date("2013-09-25") to determine
whether to update the field:
db.tags.updateOne( { _id: 1 }, { $min: { dateEntered: new Date("2013-09-25") } } )
The operation updates the dateEntered field:
{ _id: 1, desc: "crafts", dateEntered: ISODate("2013-09-25T00:00:00Z"), dateExpired: ISODate("2013-10-01T16:38:16Z") }