Can I use… case … when … (simple)


Apache DerbyBigQueryDb2 (LUW)H2MariaDBMySQLOracle DBPostgreSQLSQL ServerSQLite200520072009201120132015201720192021✓ 3.5.7+✓ 2008R2+✓ 8.3+✓ 11gR1+✓ 5.0+✓ 5.1+✓ 1.4.191+✓ 9.7+✓ 2.0+✓ 10.15.1.3+

Case is a conditional SQL expression: It searches for the first when clause whose value equals (=) that of the case clause and returns the value of the corresponding then clause—or that of else if nothing matches or null if there is no else clause.

SELECT CASE <expr> WHEN 0 THEN 'zero'
                   WHEN 1 THEN 'one'
                   ELSE 'not zero or one'
        END
  FROM …

Note that when null never matches. Use case when <expr> is null instead.

Normative References

The simple case expression is defined in ISO/IEC 9075:2016-2 as mandatory feature F261-01.

About the Author

Photo of Markus Winand

Markus Winand is the SQL Renaissance Ambassador. He is on a mission to introduce developers to the evolution of SQL in the 21st century. Markus can be hired as trainer, speaker and consultant via winand.at.

Buy his Book

Cover of “SQL Performance Explained”: Squirrel running on grass

The essence of SQL tuning in 200 pages

Buy now!
(paperback and/or PDF)

Paperback also available at Amazon.com.

Hire Markus

Markus offers SQL training and consulting for developers working at companies of any size.
Learn more »

Connect with Markus Winand

Markus Winand on LinkedInMarkus Winand on XINGMarkus Winand on Twitter
“modern SQL” by Markus Winand is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Unported License.
Legal | Contact | NO WARRANTY | Trademarks | Privacy and GDPR | CC-BY-NC-ND 3.0 license