PostgreSQL CASE Expression
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
Return specific values if the price meets a specific condition:
SELECT product_name,
CASE
WHEN price < 10 THEN 'Low price product'
WHEN price > 50 THEN 'High price product'
ELSE
'Normal product'
END
FROM products;
Run Example »
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
Same example, but with an alias for the case column::
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;
Run Example »
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.