MySQL
- Introduction To MySQL
- MySQL RDBMS
- MySQL SQL
- MySQL SELECT Statement
- MySQL WHERE Clause
- MySQL AND, OR And NOT Operators
- MySQL ORDER BY Keyword
- MySQL INSERT INTO Statement
- MySQL NULL Values
- MySQL UPDATE Statement
- MySQL DELETE Statement
- MySQL LIMIT Clause
- MySQL MIN() And MAX() Functions
- MySQL COUNT(), AVG() And SUM() Functions
- MySQL LIKE Operator
- MySQL Wildcards
- MySQL IN Operator
- MySQL BETWEEN
- MySQL Aliases
- MySQL Joins
- MySQL INNER JOIN Keyword
- MySQL LEFT JOIN Keyword
- MySQL RIGHT JOIN Keyword
- MySQL CROSS JOIN Keyword
- MySQL Self Join
- MySQL UNION Operator
- MySQL GROUP BY Statement
- MySQL HAVING Clause
- MySQL EXISTS Operator
- MySQL ANY And ALL Operators
- MySQL INSERT INTO SELECT Statement
- MySQL CASE Statement
- MySQL NULL Functions
- MySQL Comments
- MySQL Operators
- MySQL CREATE DATABASE Statement
- MySQL DROP DATABASE Statement
- MySQL CREATE TABLE Statement
- MySQL DROP TABLE Statement
- MySQL ALTER TABLE Statement
- MySQL Constraints
- MySQL NOT NULL Constraint
- MySQL UNIQUE Constraint
- MySQL PRIMARY KEY Constraint
- MySQL FOREIGN KEY Constraint
- MySQL CHECK Constraint
- MySQL DEFAULT Constraint
- MySQL CREATE INDEX Statement
- MySQL AUTO INCREMENT Field
- MySQL Working With Dates
- MySQL Views
- MySQL Data Types
- MySQL Functions
MySQL CASE Statement
The MySQL CASE Statement
The CASE statement 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 Syntax
CASE
WHEN condition1 THEN result1
WHEN condition2 THEN result2
WHEN conditionN THEN resultN
ELSE result
END;
WHEN condition1 THEN result1
WHEN condition2 THEN result2
WHEN conditionN THEN resultN
ELSE result
END;
Demo Database
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 |
MySQL CASE Examples
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;
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);
FROM Customers
ORDER BY
(CASE
WHEN City IS NULL THEN Country
ELSE City
END);