In PostgreSQL, we can use the lower() function to convert uppercase characters to their lowercase equivalent, according to the rules of the database’s locale.

Syntax

The syntax goes like this:

lower ( text )

Where text is the text to be converted to lowercase.

Example

SELECT lower('MOUSE');

Result:

mouse

Any lowercase characters remain lowercase, while uppercase characters are converted to lowercase:

SELECT lower('Mouse');

Result:

mouse

Database Example

Here’s an example of converting the results of a database query to lowercase:

SELECT 
    first_name,
    LOWER(first_name)
FROM actor
LIMIT 10;

Result:

+------------+-----------+
| first_name |   lower   |
+------------+-----------+
| PENELOPE   | penelope  |
| NICK       | nick      |
| ED         | ed        |
| JENNIFER   | jennifer  |
| JOHNNY     | johnny    |
| BETTE      | bette     |
| GRACE      | grace     |
| MATTHEW    | matthew   |
| JOE        | joe       |
| CHRISTIAN  | christian |
+------------+-----------+

Here I used the pagila sample database. This database stores actors first names in uppercase characters in the first_name column. Therefore I used the lower() function to convert the first_name column to its lowercase equivalent.

To convert the other way around (from lowercase to uppercase), we can use upper().