SQL COALESCE Function Explained Briefly | Generated by AI

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Question: What is COALESCE in SQL — if value is not null use that value, if null then use ''?

Answer:

COALESCE(expr, fallback) returns the first non-NULL argument in its argument list.

SELECT COALESCE(some_column, '') AS safe_value
FROM my_table;

• If some_column is 'hello' → returns 'hello'
• If some_column is NULL → returns ''

It short-circuits — stops at the first non-NULL. You can chain multiple fallbacks:

SELECT COALESCE(nickname, full_name, email, 'Unknown') AS display_name
FROM users;

Works across PostgreSQL, MySQL, SQLite, SQL Server, Oracle — it’s ANSI SQL standard.

Alternative (MySQL-specific): IFNULL(expr, '') — same behavior but only takes 2 args.

Alternative (SQL Server): ISNULL(expr, '') — same, 2 args only.

COALESCE is the portable one to default to.

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