Can I Use IF Statements in MS SQL WHERE Clauses?

Using IF statement in MS SQL WHERE clause

Is it possible to embed an IF statement in the WHERE clause of MS SQL? For example, is the following syntax valid?

<code class="language-sql">WHERE
    IF IsNumeric(@OrderNumber) = 1
        OrderNumber = @OrderNumber
    ELSE
        OrderNumber LIKE '%' + @OrderNumber + '%'</code>

Solution:

The above syntax is invalid. The same functionality can be achieved using the CASE statement:

<code class="language-sql">WHERE OrderNumber LIKE
  CASE WHEN IsNumeric(@OrderNumber) = 1 THEN 
    @OrderNumber 
  ELSE
    '%' + @OrderNumber + '%'
  END</code>

Alternatively, an IF statement can be used, but within a stored procedure or other control flow structure:

<code class="language-sql">IF IsNumeric(@OrderNumber) = 1
BEGIN
    SELECT * FROM YourTable WHERE OrderNumber = @OrderNumber;
END
ELSE
BEGIN
    SELECT * FROM YourTable WHERE OrderNumber LIKE '%' + @OrderNumber + '%';
END</code>

It should be noted that using the IF statement directly in the WHERE clause is not allowed. The CASE statement provides a more concise and SQL-compliant way to handle conditional logic. If you need to use an IF statement, you must place it in a stored procedure or other environment that allows control flow statements.

The above is the detailed content of Can I Use IF Statements in MS SQL WHERE Clauses?. For more information, please follow other related articles on the PHP Chinese website!