NULL Handling in SQL
From the SQL cheat sheet · CASE & NULL Handling · verified Jul 2026
NULL Handling
Check, replace, and handle NULL values safely.
sql
-- Check for NULL
SELECT * FROM users WHERE phone IS NULL;
SELECT * FROM users WHERE phone IS NOT NULL;
-- COALESCE — first non-NULL value
SELECT COALESCE(nickname, first_name, 'Unknown') AS display_name
FROM users;
-- NULLIF — returns NULL if values are equal
SELECT NULLIF(discount, 0) FROM products;💡 COALESCE is standard SQL and works on all databases — prefer it over IFNULL/ISNULL
⚡ NULLIF(x, 0) prevents division-by-zero errors by returning NULL instead
📌 NULL is not equal to anything — even NULL = NULL is false, always use IS NULL
🟢 Aggregate functions (AVG, SUM, COUNT(col)) automatically skip NULL values
nullcoalescenullifis-null