IsNull

Return TRUE if the expression is NULL, otherwise return FALSE.

Syntax
      IsNull(expression)

Key
   expression    A string or numeric expression.

The IsNull() function can be used in VBA or in an SQL query.

MS Access makes a distinction between an empty string "" and a NULL value. If you type something into a field and then delete it, you will be left with a zero length string, in contrast if nothing has ever been entered into a field it will be NULL. IsNull() will only detect NULLs.

Examples

In a query:

IsNull

In SQL queries it is also useful to use the SQL IS operator with Null to find Null values:

Is NULL

In VBA:

Dim boolDemo as Boolean
boolDemo = IsNull(Me!txtDescription)
If boolDemo = True Then Msgbox "A required value is missing!"

“Art is the elimination of the unnecessary” ~ Pablo Picasso

Related:

Nz - Detect a NULL or a Zero Length string.
IsEmpty - Test if an expression is Empty (unassigned).


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