CASE
The CASE expression goes through conditions and returns a value when the first condition is met (like an if-then-else statement).
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.
Example
SELECT product_name,
CASE
WHEN price < 10 THEN 'Low price product'
WHEN price > 50 THEN 'High
price product'
ELSE
'Normal product'
END
FROM
products;
With an Alias
When a column name is not specified for the "case" field, the parser uses case as the column name.
To specify a column name, add an alias after the END keyword.
Example
SELECT product_name,
CASE
WHEN price < 10 THEN 'Low price product'
WHEN price > 50 THEN 'High
price product'
ELSE
'Normal product'
END AS "price category"
FROM
products;
You can read more about aliases in our PostgreSQL AS chapter.
