CASE statement in SQL, The case statement in SQL returns a value on a specified condition. We can use a Case statement in select queries along with Where, Order By and Group By clause, The CASE statement goes through conditions and returns a value when the first condition is IF-THEN-ELSE statement. So, once a condition is true, it will stop reading and return the result. If no conditions are true, it returns the value in the ELSE clause. A CASE statement can return only one value. CASE by definition only returns a single value.
CASE
WHEN condition1 THEN result1
WHEN condition2 THEN result2
WHEN condition3 THEN result3
WHEN conditionN THEN resultN
ELSE result
END
Example
SELECT CName, City, Country
FROM Customer
ORDER BY
(CASE
WHEN City IS NULL THEN Country
ELSE City
END)
2020-05-11