How Can I Replicate CASE Expressions in Microsoft Access?

Simulating CASE Statements in Microsoft Access

Microsoft Access lacks direct support for CASE expressions. However, we can achieve similar conditional logic using alternative functions.

Using the IIF() Function

The IIF() function offers a simple way to replicate basic CASE statements:

<code class="language-sql">IIF(condition, true_result, false_result)</code>

• condition: The Boolean expression to evaluate.
• true_result: The value returned if the condition is TRUE.
• false_result: The value returned if the condition is FALSE.

Example: Finding the later date between two fields:

<code class="language-sql">IIF(dbo_tbl_property.LASTSERVICEDATE > Contour_dates.[Last CP12 Date], dbo_tbl_property.LASTSERVICEDATE, Contour_dates.[Last CP12 Date])</code>

Employing the Switch() Function

For scenarios with multiple conditions, the Switch() function provides a more elegant solution:

<code class="language-sql">Switch(expr1, value1, expr2, value2, ..., exprN, valueN)</code>

Switch() evaluates expressions sequentially. It returns the value associated with the first expression that evaluates to TRUE. Key points to remember:

• Expressions and values must be paired.
• All expressions are evaluated, regardless of whether a TRUE result is found earlier.
• If no expression is TRUE, or the associated value is Null, Switch() returns Null.

This approach allows for creating complex conditional logic within Microsoft Access queries, effectively mirroring the functionality of CASE statements found in other database systems.

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