How Can I Rewrite IS DISTINCT FROM and IS NOT DISTINCT FROM Operators in SQL Server 2008R2?

Rewriting the IS DISTINCT FROM operator in SQL Server 2008R2

SQL Server 2008R2 does not support the standard IS DISTINCT FROM and IS NOT DISTINCT FROM operators. This article provides a solution to rewrite these expressions using an alternative syntax that is compatible with this version of the software.

IS DISTINCT FROM

The IS DISTINCT FROM predicate evaluates to True if the two values ​​are not equal or one of the values ​​is NULL; it evaluates to False if they are equal and neither is NULL. It can be rewritten as follows:

<code class="language-sql">((a != b OR a IS NULL OR b IS NULL) AND NOT (a IS NULL AND b IS NULL))</code>

Example:

<code class="language-sql">SELECT CASE
    WHEN (a != b OR a IS NULL OR b IS NULL) AND NOT (a IS NULL AND b IS NULL) THEN 'True'
    ELSE 'False'
END AS DistinctResult</code>

IS NOT DISTINCT FROM

The

IS NOT DISTINCT FROM operator evaluates to True if the two values ​​are equal or both are NULL, and evaluates to False if they are not equal and not both NULL. It can be rewritten as:

<code class="language-sql">(NOT (a != b OR a IS NULL OR b IS NULL) OR (a IS NULL AND b IS NULL))</code>

Example:

<code class="language-sql">SELECT CASE
    WHEN (NOT (a != b OR a IS NULL OR b IS NULL) OR (a IS NULL AND b IS NULL)) THEN 'True'
    ELSE 'False'
END AS NotDistinctResult</code>

Note:

The provided override ensures that the result is always True or False, avoiding the Unknown state that can occur with NULL operands.

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