The MySQL GREATEST() function is a comparison function that returns the largest value from a list of values.

The list of values is provided as multiple arguments. So in other words, GREATEST() returns the maximum-valued argument from a list of arguments.

Syntax

The syntax of GREATEST() goes like this:

GREATEST(value1,value2,...)

Each argument is separated by a comma. This function compares them all and returns the one with the largest value.

Example 1 – Comparing Numbers

If all arguments are integers, they’re compared as integers.

SELECT GREATEST(12, 120, 2400) AS 'Result';

Result:

+--------+
| Result |
+--------+
|   2400 |
+--------+

If at least one argument is double precision, they are compared as double-precision values. Otherwise, if at least one argument is a DECIMAL value, they are compared as DECIMAL values.

SELECT GREATEST(12.00, 120, 2400) AS 'Result';

Result:

+---------+
| Result  |
+---------+
| 2400.00 |
+---------+

See below for the exact rules for determining the return value.

Example 2 – Comparing Strings

Here’s an example of comparing strings.

SELECT GREATEST('a', 'b', 'c') AS 'Result';

Result:

+--------+
| Result |
+--------+
| c      |
+--------+

Here’s another one:

SELECT GREATEST('Cat', 'Dogg', 'Rat') AS 'Result';

Result:

+--------+
| Result |
+--------+
| Rat    |
+--------+

Example 3 – NULL Values

If any of the arguments is NULL, the result is NULL.

SELECT GREATEST('a', NULL, 'c') AS 'Result';

Result:

+--------+
| Result |
+--------+
| NULL   |
+--------+

Comparison Rules

Certain rules are applied when determining what the return value will be. These rules are as follows:

• If any argument is NULL, the result is NULL. No comparison is needed.
• If all arguments are integer-valued, they are compared as integers.
• If at least one argument is double precision, they are compared as double-precision values. Otherwise, if at least one argument is a DECIMAL value, they are compared as DECIMAL values.
• If the arguments comprise a mix of numbers and strings, they are compared as numbers.
• If any argument is a nonbinary (character) string, the arguments are compared as nonbinary strings.
• In all other cases, the arguments are compared as binary strings.