Finding the Maximum Date in Microsoft Access with IIF() and Switch()

Microsoft Access doesn't directly support CASE expressions. However, we can achieve similar functionality for determining maximum dates using the IIF() and Switch() functions.

The IIF() Function

The IIF() function is a conditional statement that returns one value if a condition is true, and another if it's false. Its structure is:

IIF(condition, true_value, false_value)

Example: To find the maximum date between two fields, LASTSERVICEDATE and [Last CP12 Date]:

IIF(dbo_tbl_property.LASTSERVICEDATE > Contour_dates.[Last CP12 Date], dbo_tbl_property.LASTSERVICEDATE, Contour_dates.[Last CP12 Date]) AS MaxDate

This query returns LASTSERVICEDATE if it's greater than [Last CP12 Date]; otherwise, it returns [Last CP12 Date].

The Switch() Function

The Switch() function provides a more concise way to handle multiple conditions. Its syntax is:

Switch(expr1, value1, expr2, value2, ..., exprN, valueN)

The function evaluates expressions sequentially. If an expression evaluates to true, the corresponding value is returned.

Example: Using Switch() to find the maximum date:

Switch(dbo_tbl_property.LASTSERVICEDATE > Contour_dates.[Last CP12 Date], dbo_tbl_property.LASTSERVICEDATE, TRUE, Contour_dates.[Last CP12 Date]) AS MaxDate

This achieves the same result as the IIF() example. Note that Switch() evaluates all expressions, even after a true condition is found. Be mindful of potential errors like division by zero that might arise from this behavior.

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