Case statements

Often, we want to display data based on some sort of condition. In these situations, a case statement can be used to display data relative to a condition. The case statement syntax is shown here:

CASE WHEN [condition 1] THEN [result1]
WHEN [condition 2] THEN [result2]
…
[ELSE] [resultn]
END

For example, suppose that you had a table of users named userTable, which contained users of varying ages. If a user is age 18 or older, you want to show them as an adult. If a user is younger than age 18, you want to show them as a youth. To achieve this, you can use a case statement, like so:

SELECT CASE WHEN age >= 18 THEN ‘adult’
ELSE ‘youth’ END AS isadult FROM user;

The next exercise demonstrates a practical example of case statements.