Case expressions in Access

Can you use case expressions in Access? I’m trying to determine the max date form 2 columns but keep getting syntax errors in the following code:

CASE 
  WHEN dbo_tbl_property.LASTSERVICEDATE > Contour_dates.[Last CP12 Date]
    THEN dbo_tbl_property.LASTSERVICEDATE 
  ELSE Contour_dates.[Last CP12 Date] 
END AS MaxDate

Answer

You can use the IIF() function instead.

IIF(condition, valueiftrue, valueiffalse)

• condition is the value that you want to test.

• valueiftrue is the value that is returned if condition evaluates to TRUE.

• valueiffalse is the value that is returned if condition evaluates to FALSE.

There is also the Switch function which is easier to use and understand when you have multiple conditions to test:

Switch( expr-1, value-1 [, expr-2, value-2 ] … [, expr-n, value-n ] )

The Switch function argument list consists of pairs of expressions and values. The expressions are evaluated from left to right, and the value associated with the first expression to evaluate to True is returned. If the parts aren’t properly paired, a run-time error occurs. For example, if expr-1 is True, Switch returns value-1. If expr-1 is False, but expr-2 is True, Switch returns value-2, and so on.

Switch returns a Null value if:

• None of the expressions is True.

• The first True expression has a corresponding value that is Null.

NOTE: Switch evaluates all of the expressions, even though it returns only one of them. For this reason, you should watch for undesirable side effects. For example, if the evaluation of any expression results in a division by zero error, an error occurs.