How to get min/max of two integers in Postgres/SQL?

Question

How do I find the maximum (or minimum) of two integers in Postgres/SQL? One of the integers is not a column value.

I will give an example scenario:

I would like to subtract an integer from a column (in all rows), but the result should not be less than zero. So, to begin with, I have:

UPDATE my_table
SET my_column = my_column - 10;

But this can make some of the values negative. What I would like (in pseudo code) is:

UPDATE my_table
SET my_column = MAXIMUM(my_column - 10, 0);

Relatedly you can create a union data set and then max that, in sql-server at least stackoverflow.com/questions/124417/… — Kzqai
– Kzqai, Commented Mar 28, 2020 at 18:31

Mark Byers · Accepted Answer · 2015-01-08 15:35:16Z

538

UPDATE my_table
SET my_column = GREATEST(my_column - 10, 0);

user330315

answered May 29, 2010 at 19:42

Mark Byers

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Comments

ThiefMaster · Accepted Answer · 2016-04-21 15:11:34Z

24

You want the inline sql case:

set my_column = case when my_column - 10 > 0 then my_column - 10 else 0 end

max() is an aggregate function and gets the maximum of a row of a result set.

Edit: oops, didn't know about greatest and least in postgres. Use that instead.

ThiefMaster

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answered May 29, 2010 at 19:41

Donnie

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This version is useful if you're restricted to standard SQL.