$nin

Definition

Negates array membership.

Expression operator · Comparison · Studio Visual: not exposed. Studio validates the complete expression separately.

Syntax

{ "$nin": [ <value>, <array> ] }

Replace angle-bracket placeholders with expressions or values.

Optional parameters may be omitted.

Parameters

Parameter	Required	Description
value	Yes	Expression supplying the value to evaluate.
array	Yes	Expression supplying the source array.

Arguments are positional: keep the order shown. The authoring signature accepts 2–2 arguments.

Behavior

The following observations use the example expression below. Each row substitutes one argument while retaining the other example arguments. A missing field differs from an explicit null; the result shown is what Core actually returned.

For the value argument:

Input case	Supplied value	Result
null	null	true
missing	Field absent	true
decimal	2.5	true
numeric string	"12"	true
text	"hello"	true
boolean	true	true
typed date	{"$date":"2026-01-15T15:00:00Z"}	true
empty array	[]	true
numeric array	[1,2,3]	true
object	{"x":1}	true

Argument handling

Invocation	Result
{"$nin":[]}	Error — $in expects [searchExpr, candidates]
{"$nin":{"unexpected":1}}	Error — $in expects [searchExpr, candidates]

Examples

Expression:

{
  "$nin": [
    2,
    [
      1,
      2
    ]
  ]
}

Input document:

{}

Observed SrotaX result: false.

Detailed input cases

Expand the complete argument-by-argument test matrix

Each table changes only the indicated argument from the example above. Other arguments retain their baseline values. Values normally come from the input field probe; literal configuration arguments are replaced directly. “Missing” means the field is absent, not explicitly null. Numeric strings are strings, not numbers.

Argument: value[0]

Input case	Supplied value	SrotaX result
null	null	true
missing	Field absent	true
zero	0	true
negative	-2	true
decimal	2.5	true
numeric string	"12"	true
text	"hello"	true
empty string	""	true
boolean	true	true
false	false	true
typed date	{"$date":"2026-01-15T15:00:00Z"}	true
decimal128	{"$numberDecimal":"1.25"}	true
empty array	[]	true
numeric array	[1,2,3]	true
mixed array	[1,null,"x",3]	true
nested array	[[1,2],[3]]	true
empty object	{}	true
object	{"x":1}	true
ISO date string	"2026-01-15T15:00:00Z"	true

Argument: array[1]

Input case	Supplied value	SrotaX result
null	null	Error — $in requires the second argument to evaluate to an array
missing	Field absent	Error — $in requires the second argument to evaluate to an array
zero	0	Error — $in requires the second argument to evaluate to an array
negative	-2	Error — $in requires the second argument to evaluate to an array
decimal	2.5	Error — $in requires the second argument to evaluate to an array
numeric string	"12"	Error — $in requires the second argument to evaluate to an array
text	"hello"	Error — $in requires the second argument to evaluate to an array
empty string	""	Error — $in requires the second argument to evaluate to an array
boolean	true	Error — $in requires the second argument to evaluate to an array
false	false	Error — $in requires the second argument to evaluate to an array
typed date	{"$date":"2026-01-15T15:00:00Z"}	Error — $in requires the second argument to evaluate to an array
decimal128	{"$numberDecimal":"1.25"}	Error — $in requires the second argument to evaluate to an array
empty array	[]	true
numeric array	[1,2,3]	false
mixed array	[1,null,"x",3]	true
nested array	[[1,2],[3]]	true
empty object	{}	Error — $in requires the second argument to evaluate to an array
object	{"x":1}	Error — $in requires the second argument to evaluate to an array
ISO date string	"2026-01-15T15:00:00Z"	Error — $in requires the second argument to evaluate to an array

Verification

This page records 41 executed cases. It covers individual argument substitutions, not every cross-product of arguments, locale, daylight-saving transitions, numeric overflow, collation or resource limits. No untested behavior is guaranteed.

Download exact expressions, inputs and SrotaX results. Errors are observed messages, not stable public error codes. The reference generator reads the checked-in execution report; do not edit generated observations by hand.

MongoDB differences

This name is a SrotaX extension or belongs to another MongoDB context. It is not compared as a MongoDB aggregation expression. This is not a missing implementation failure.