COALESCE vs ISNULL/IFNULL/NVL
COALESCE vs ISNULL / IFNULL / NVL
Null handling functions allow replacing missing (NULL) database values with a meaningful default.
Function Comparison
| Function | Supported DBMS | Arguments | Feature / Behavior |
|---|---|---|---|
| COALESCE | ANSI SQL (All DBs) | 2 or more | Returns first non-NULL argument |
| ISNULL | SQL Server (T-SQL) | Exactly 2 | Casts replacement to expr type |
| IFNULL | MySQL, SQLite | Exactly 2 | Fallback to second argument |
| NVL | Oracle | Exactly 2 | Returns second arg if first is NULL |
Why COALESCE is Preferred
- SQL Standard: Works seamlessly across PostgreSQL, MySQL, SQL Server, Oracle, and SQLite.
- Multi-argument Chaining: Evaluates expressions left-to-right with short-circuit evaluation:
CODE
SELECT COALESCE(work_phone, cell_phone, home_phone, 'No Phone') AS contact_phone FROM users; - Data Type Promotion: Returns the highest precedence data type among all arguments.