GREATEST Function in SQL

The GREATEST function returns the largest value from a list of expressions.

Syntax:

GREATEST(expr1, expr2, expr3, ...);

It compares the values and returns the greatest (maximum) one.

Behavior:

• Works with numbers, strings, and dates.

• Returns NULL if any argument is NULL in some databases (like Oracle).

• Not supported in some SQL flavors (like SQL Server) — alternatives exist.

Examples:

1. Numbers

SELECT GREATEST(10, 20, 5) AS max_value;  -- Returns 20

2. Strings (compared lexicographically)

SELECT GREATEST('apple', 'banana', 'pear') AS greatest_fruit;-- Returns 'pear' (since 'pear' > 'banana' > 'apple' lex order)

3. Dates

SELECT GREATEST(DATE '2025-01-01', DATE '2024-12-31') AS latest_date;-- Returns 2025-01-01

Notes by SQL Flavor:

SQL Server alternative (no GREATEST function):

SELECT   (SELECT MAX(v) FROM (VALUES (10), (20), (5)) AS value(v)) AS max_value;

If you want, I can help you write a query with GREATEST for your specific use case or SQL database!