[MongoDB] How do I query for fields that have null values?

{Column: NULL}: The result is that the column value is null or the record does not contain the column field data;

{Column: {$ type: 10 }}: the result is data that contains the column field and the value is null;

{Column :{$ exists: false }}: the result is data that does not contain the column field;

Fields in a document may storeNullValues, as in a notional collection,Test, With the following tables ents:

{ _ Id: 1, Canceldate: Null }{ _ Id: 2 }
 

Different query operators treatNullValues differently:

• The{ Canceldate : Null }Query matches documents that either containsCanceldateField whose value isNull OrThat do not containCanceldateField:

   
  DB.Test.Find( { Canceldate: Null } )
   

  The query returns both statements ents:

   {  "_ id"  :   1  ,   "canceldate"  :   null  } {< /span>  "_ id"  :   2  } 

• the { canceldate : { $ type: 10 } }< /span> query matches documents that contains the canceldate Field whose value is null only ; i. e. the value of the canceldate field is of bson type null (I. e. 10 ):

  DB.Test.Find( { Canceldate : { $ Type: 10 } } )
   

  The query returns only the document that containsNullValue:

   
  { "_ Id" : 1, "Canceldate" : Null }
   

• The{ Canceldate : { $ Exists: False } }Query matches documents that do not contain inCanceldateField:

   
  DB.Test.Find( { Canceldate : { $ Exists: False } } )
   

  The query returns only the document that doesNotContainCanceldateField:

   
  { "_ Id" : 2 }
   

See also

 

The reference documentation for$ TypeAnd$ ExistsOperators.