I’m working on a MySQL database and need help with checking for both NULL values and empty strings in a column. Right now I have a basic query that only handles NULL values:
SELECT COALESCE(username, 'no_value') as username from users
But this doesn’t catch empty strings. I want to modify it so it also checks for empty strings (not just NULL). I tried something like this but it’s not working:
SELECT COALESCE(username, 'no_value') AND username != '' as username from users
What’s the correct way to check for both conditions in a single MySQL statement? I need the query to return ‘no_value’ when the username field is either NULL or contains an empty string.
You could also use a CASE statement for more control: SELECT CASE WHEN username IS NULL OR username = '' THEN 'no_value' ELSE username END as username FROM users. I find this way easier to debug, especially when I need to add more conditions later. The CASE statement shows exactly what you’re checking for - way more readable than nested functions. Performance is about the same as NULLIF, maybe slightly faster since there’s no function calls.
Here’s another approach using LENGTH with COALESCE: SELECT COALESCE(NULLIF(TRIM(username), ''), 'no_value') as username FROM users. This catches whitespace-only strings too - super common with user input. I’ve been burned by this before when users just entered spaces and my queries missed them. TRIM strips the whitespace first, then checks if there’s anything left. Really handy for form inputs where people accidentally add spaces. Performance is about the same as other solutions, but you get extra data validation that’ll save you headaches later.
Try NULLIF with COALESCE: SELECT COALESCE(NULLIF(username, ''), 'no_value') as username FROM users - NULLIF turns empty strings into null, then COALESCE catches both null and empty cases. Works perfectly!