HTML tutorial
CSS3 tutorial
Bootstrap tutorial
JavaScript tutorial
JQuery tutorial
AngularJS tutorial
React tutorial
NodeJS tutorial
PHP tutorial
Python tutorial
Python3 tutorial
Django tutorial
Linux tutorial
Docker tutorial
Ruby tutorial
Java tutorial
C tutorial
C ++ tutorial
Perl tutorial
JSP tutorial
Lua tutorial
Scala tutorial
Go tutorial
ASP.NET tutorial
C # tutorial
The CASE expression goes through conditions and returns a value when the first condition is met (like an 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
The CASE
expression goes through conditions and returns a value when the first condition is
met (like an 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.
If there is no ELSE
part and no conditions are true, it returns NULL.
CASE
WHEN condition1 THEN result1
WHEN condition2 THEN result2
WHEN
conditionN THEN resultN
ELSE result
END;
Below is a selection from the "OrderDetails" table in the Northwind sample database:
OrderDetailID | OrderID | ProductID | Quantity |
---|---|---|---|
1 | 10248 | 11 | 12 |
2 | 10248 | 42 | 10 |
3 | 10248 | 72 | 5 |
4 | 10249 | 14 | 9 |
5 | 10249 | 51 | 40 |
The following SQL goes through conditions and returns a value when the first condition is met:
SELECT OrderID, Quantity,
CASE
WHEN Quantity > 30
THEN 'The quantity is greater than 30'
WHEN Quantity = 30 THEN 'The
quantity is 30'
ELSE 'The quantity is under 30'
END AS QuantityText
FROM OrderDetails;
The following SQL will order the customers by City. However, if City is NULL, then order by Country:
SELECT CustomerName, City, Country
FROM Customers
ORDER BY
(CASE
WHEN City IS NULL THEN Country
ELSE City
END);