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- $toLower (aggregation)
$toLower (aggregation)¶
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Definition¶
- $toLower¶
Converts a string to lowercase, returning the result.
$toLower has the following syntax:
{ $toLower: <expression> }
The argument can be any expression as long as it resolves to a string. For more information on expressions, see Expressions.
If the argument resolves to null, $toLower returns an empty string "".
Behavior¶
$toLower only has a well-defined behavior for strings of ASCII characters.
Example¶
Consider a inventory collection with the following documents:
{ "_id" : 1, "item" : "ABC1", quarter: "13Q1", "description" : "PRODUCT 1" }
{ "_id" : 2, "item" : "abc2", quarter: "13Q4", "description" : "Product 2" }
{ "_id" : 3, "item" : "xyz1", quarter: "14Q2", "description" : null }
The following operation uses the $toLower operator return lowercase item and lowercase description value:
db.inventory.aggregate(
[
{
$project:
{
item: { $toLower: "$item" },
description: { $toLower: "$description" }
}
}
]
)
The operation returns the following results:
{ "_id" : 1, "item" : "abc1", "description" : "product 1" }
{ "_id" : 2, "item" : "abc2", "description" : "product 2" }
{ "_id" : 3, "item" : "xyz1", "description" : "" }
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