Litware Price Groups: In the first T-SQL snippet, which keyword should begin the CASE expression inside the SELECT?

• A. WHEN
• B. CASE
• C. THEN
• D. END

Answer: (B)

The CASE expression in T-SQL is started with the keyword CASE inside a SELECT. That first token signals the beginning of the conditional expression you’re building. After CASE, you supply branches with WHEN ... THEN ... for each condition, and finally END to close the expression. So the keyword that should begin the CASE expression is CASE.

For example:

SELECT CASE WHEN Amount > 1000 THEN 'High' ELSE 'Low' END AS PriceGroup FROM Orders;

Here you see CASE opens the expression, WHEN defines a condition, THEN specifies the result for that condition, and END closes it. The other keywords come after the initial CASE, so they can’t start the expression.