COALESCE vs ISNULL portability

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Accepted Answer

COALESCE is defined by the SQL standard and works in PostgreSQL, MySQL, SQL Server, Oracle, and SQLite. ISNULL is a SQL Server and Sybase proprietary function that takes exactly two arguments and always returns the data type of the first argument. NVL is Oracle-specific, and IFNULL is MySQL/SQLite-specific. When writing portable SQL, always prefer COALESCE over any vendor-specific two-argument NULL replacement function.