GREATEST and LEAST functions - Amazon Redshift
SyntaxParametersReturnsExample
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GREATEST and LEAST functions

Returns the largest or smallest value from a list of any number of expressions.

Syntax

GREATEST (value [, ...])
LEAST (value [, ...])

Parameters

expression_list

A comma-separated list of expressions, such as column names. The expressions must all be convertible to a common data type. NULL values in the list are ignored. If all of the expressions evaluate to NULL, the result is NULL.

Returns

Returns the greatest (for GREATEST) or least (for LEAST) value from the provided list of expressions.

Example

The following example returns the highest value alphabetically for firstname or lastname.

select firstname, lastname, greatest(firstname,lastname) from users
where userid < 10
order by 3;

 firstname | lastname  | greatest
-----------+-----------+-----------
 Lars      | Ratliff   | Ratliff
 Reagan    | Hodge     | Reagan
 Colton    | Roy       | Roy
 Barry     | Roy       | Roy
 Tamekah   | Juarez    | Tamekah
 Rafael    | Taylor    | Taylor
 Victor    | Hernandez | Victor
 Vladimir  | Humphrey  | Vladimir
 Mufutau   | Watkins   | Watkins
(9 rows)