$substr (aggregation)
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Definition
-
$substr
-
Deprecated since version 3.4:
$substr
is now an alias for$substrBytes
.Returns a substring of a string, starting at a specified index position and including the specified number of characters. The index is zero-based.
$substr
has the following syntax:The arguments can be any valid expression as long as the first argument resolves to a string, and the second and third arguments resolve to integers. For more information on expressions, see Expressions.
Behavior
If <start>
is a negative number, $substr
returns an empty string ""
.
If <length>
is a negative number, $substr
returns a substring that starts at the specified index and includes the rest of the string.
$substr
only has a well-defined behavior for strings of ASCII characters.
Example
Consider an inventory
collection with the following documents:
The following operation uses the $substr
operator to separate the quarter
value into a yearSubstring
and a quarterSubstring
:
The operation returns the following results: