SQL COALESCE returns the first non-NULL value from a list of expressions, letting you set reliable fallbacks, replace NULLs in results, and simplify CASE logic in SELECT, WHERE, ORDER BY, and GROUP BY clauses across PostgreSQL, MySQL, SQL Server, and other ANSI-SQL databases.
SQL COALESCE is a scalar function that scans its arguments from left to right and returns the first value that is not NULL.
COALESCE evaluates expressions in order and stops once it finds a non-NULL value, ensuring only one evaluation per position. This short-circuit behavior is ANSI-SQL compliant and supported by PostgreSQL, MySQL, SQL Server, Oracle, and SQLite.
Leaving NULLs risks misleading aggregates, unreadable reports, and broken joins. COALESCE lets you surface zeros, empty strings, or fallback columns so dashboards, APIs, and downstream models stay consistent.
Choose COALESCE for simple fallback logic because it is shorter, easier to read, and often performs the same as CASE. Use CASE only when conditional logic goes beyond checking for NULL.
Yes. You can pass any number of arguments: COALESCE(col1, col2, col3, 'N/A'). The function returns the first non-NULL value among them.
COALESCE returns the data type with the highest precedence among its arguments. In mixed-type lists, cast lower-precedence types explicitly to avoid unintended promotion.
Wrap nullable columns to guarantee a value for every row. Example: SELECT COALESCE(discount_price, list_price) AS price returns list_price when discount_price is NULL.
COALESCE keeps predicates simple. WHERE COALESCE(deleted_at, '2999-12-31') > NOW() treats NULL timestamps as active records without complicated OR logic.
Yes. Use COALESCE on join keys when data can reside in multiple columns. Example: joining contacts on COALESCE(phone_mobile, phone_home) ensures a valid key even if one column is NULL.
Aggregates ignore NULLs, so wrapping columns with COALESCE converts them to zeros or placeholders, letting SUM, AVG, and COUNT behave predictably.
Absolutely. ORDER BY COALESCE(last_login, created_at) sorts users consistently. GROUP BY works the same way but ensure all grouped columns share identical COALESCE expressions in SELECT.
COALESCE is lightweight. It may prevent index usage if applied directly to indexed columns. Instead, create computed columns or use IS NULL checks when performance is critical.
Always specify an explicit default, cast mixed types, limit to essential columns, and avoid masking data issues by documenting why NULLs appear.
IFNULL (MySQL) and NVL (Oracle) accept exactly two arguments. COALESCE is portable ANSI SQL and supports multiple arguments, making it safer for cross-database code.
Galaxys AI copilot auto-suggests COALESCE patterns, warns about datatype mismatches, and rewrites legacy IFNULL/NVL calls to ANSI-standard COALESCEspeeding up query authoring.
COALESCE is the go-to ANSI function for replacing NULLs, simplifying logic, and keeping datasets clean. Combine it with Galaxys modern editor and AI copilot to write robust, readable SQL faster.
Yes. COALESCE is part of the ANSI-SQL standard, making it portable across most relational databases.
There is no practical limit aside from database constraints. Pass as many expressions as needed until you reach a guaranteed non-NULL value.
Minimal. The function is computed per row with short-circuit logic. Only be cautious when it disables index usage on large tables.
IFNULL is a two-argument MySQL alias. COALESCE is more flexible, supports multiple arguments, and works in PostgreSQL, SQL Server, Oracle, and others.
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