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- $mul
$mul¶
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Definition¶
-
$mul
¶ New in version 2.6.
Multiply the value of a field by a number. To specify a
$mul
expression, use the following prototype:The field to update must contain a numeric value.
To specify a
<field>
in an embedded document or in an array, use dot notation.
Behavior¶
If the field does not exist in a document, $mul
creates the
field and sets the value to zero of the same numeric type as the
multiplier.
Multiplication with values of mixed numeric types (32-bit integer, 64-bit integer, float) may result in conversion of numeric type. See Multiplication Type Conversion Rules for details.
$mul
is an atomic operation within a single document.
Examples¶
Multiply the Value of a Field¶
Consider a collection products
with the following document:
The following db.collection.update()
operation updates the
document, using the $mul
operator to multiply the value in
the price
field by 1.25
:
The operation results in the following document, where the new value of
the price
field 13.7375
reflects the original value 10.99
multiplied by 1.25
:
Apply $mul
Operator to a Non-existing Field¶
Consider a collection products
with the following document:
The following db.collection.update()
operation updates the
document, applying the $mul
operator to the field price
that does not exist in the document:
The operation results in the following document with a price
field
set to value 0 of numeric type NumberLong, the same type as
the multiplier:
Multiply Mixed Numeric Types¶
Consider a collection products
with the following document:
The following db.collection.update()
operation uses the
$mul
operator to multiply the value in the price
field
NumberLong(10) by NumberInt(5):
The operation results in the following document:
The value in the price
field is of type NumberLong. See
Multiplication Type Conversion Rules for details.