Getting the minimum of two values in SQL

I have two variables, one is called PaidThisMonth, and the other is called OwedPast. They are both results of some subqueries in SQL. How can I select the smaller of the two and return it as a value titled PaidForPast?

The MIN function works on columns, not variables.

SQL Server 2012 and 2014 supports IIF(cont,true,false) function. Thus for minimal selection you can use it like

SELECT IIF(first>second, second, first) the_minimal FROM table

While IIF is just a shorthand for writing CASE...WHEN...ELSE, it's easier to write.

The solutions using CASE, IIF, and UDF are adequate, but impractical when extending the problem to the general case using more than 2 comparison values. The generalized solution in SQL Server 2008+ utilizes a strange application of the VALUES clause:

SELECT
PaidForPast=(SELECT MIN(x) FROM (VALUES (PaidThisMonth),(OwedPast)) AS value(x))

Credit due to this website: http://sqlblog.com/blogs/jamie_thomson/archive/2012/01/20/use-values-clause-to-get-the-maximum-value-from-some-columns-sql-server-t-sql.aspx

Use Case:

   Select Case When @PaidThisMonth < @OwedPast 
               Then @PaidThisMonth Else @OwedPast End PaidForPast

As Inline table valued UDF

CREATE FUNCTION Minimum
(@Param1 Integer, @Param2 Integer)
Returns Table As
Return(Select Case When @Param1 < @Param2 
                   Then @Param1 Else @Param2 End MinValue)

Usage:

Select MinValue as PaidforPast 
From dbo.Minimum(@PaidThisMonth, @OwedPast)

ADDENDUM: This is probably best for when addressing only two possible values, if there are more than two, consider Craig's answer using Values clause.

I just had a situation where I had to find the max of 4 complex selects within an update. With this approach you can have as many as you like!

You can also replace the numbers with aditional selects

select max(x)
 from (
 select 1 as 'x' union
 select 4 as 'x' union
 select 3 as 'x' union
 select 2 as 'x' 
 ) a

More complex usage

 @answer = select Max(x)
           from (
                select @NumberA as 'x' union
                select @NumberB as 'x' union
                select @NumberC as 'x' union
                select (
                       Select Max(score) from TopScores
                       ) as 'x' 
     ) a

I'm sure a UDF has better performance.

For MySQL or PostgreSQL 9.3+, a better way is to use the LEAST and GREATEST functions.

SELECT GREATEST(A.date0, B.date0) AS date0, 
       LEAST(A.date1, B.date1, B.date2) AS date1
FROM A, B
WHERE B.x = A.x

With:

• GREATEST(value [, ...]) : Returns the largest (maximum-valued) argument from values provided
• LEAST(value [, ...]) Returns the smallest (minimum-valued) argument from values provided

Documentation links :

• MySQL http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html
• Postgres https://www.postgresql.org/docs/current/functions-conditional.html

Here is a trick if you want to calculate maximum(field, 0):

SELECT (ABS(field) + field)/2 FROM Table

returns 0 if field is negative, else, return field.

Use a CASE statement.

Example B in this page should be close to what you're trying to do:
http://msdn.microsoft.com/en-us/library/ms181765.aspx

Here's the code from the page:

> USE AdventureWorks; > GO > SELECT ProductNumber, Name, 'Price Range' = > CASE > WHEN ListPrice = 0 THEN 'Mfg item - not for resale' > WHEN ListPrice < 50 THEN 'Under $50' > WHEN ListPrice >= 50 and ListPrice < 250 THEN 'Under $250' > WHEN ListPrice >= 250 and ListPrice < 1000 THEN 'Under $1000' > ELSE 'Over $1000' > END > FROM Production.Product > ORDER BY ProductNumber ; > GO

This works for up to 5 dates and handles nulls. Just couldn't get it to work as an Inline function.

CREATE FUNCTION dbo.MinDate(@Date1 datetime = Null,
							@Date2 datetime = Null,
							@Date3 datetime = Null,
							@Date4 datetime = Null,
							@Date5 datetime = Null)
RETURNS Datetime AS
BEGIN
--USAGE select dbo.MinDate('20120405',null,null,'20110305',null)
DECLARE @Output datetime;

WITH Datelist_CTE(DT)
AS (
		SELECT @Date1 AS DT WHERE @Date1 is not NULL UNION
		SELECT @Date2 AS DT WHERE @Date2 is not NULL UNION
		SELECT @Date3 AS DT WHERE @Date3 is not NULL UNION
		SELECT @Date4 AS DT WHERE @Date4 is not NULL UNION
		SELECT @Date5 AS DT WHERE @Date5 is not NULL
   )
Select @Output=Min(DT) FROM Datelist_CTE

RETURN @Output
END

Use a temp table to insert the range of values, then select the min/max of the temp table from within a stored procedure or UDF. This is a basic construct, so feel free to revise as needed.

For example:

CREATE PROCEDURE GetMinSpeed() AS
BEGIN

    CREATE TABLE #speed (Driver NVARCHAR(10), SPEED INT);
    '
    ' Insert any number of data you need to sort and pull from
    '
    INSERT INTO #speed (N'Petty', 165)
    INSERT INTO #speed (N'Earnhardt', 172)
    INSERT INTO #speed (N'Patrick', 174)

    SELECT MIN(SPEED) FROM #speed

    DROP TABLE #speed

END

Building on the brilliant logic / code from mathematix and scottyc, I submit:

DECLARE @a INT, @b INT, @c INT = 0

WHILE @c < 100
    BEGIN
	    SET @c += 1
		SET @a = ROUND(RAND()*100,0)-50
    	SET @b = ROUND(RAND()*100,0)-50
	    SELECT @a AS a, @b AS b,
		    @a - ( ABS(@a-@b) + (@a-@b) ) / 2 AS MINab,
			@a + ( ABS(@b-@a) + (@b-@a) ) / 2 AS MAXab,
    		CASE WHEN (@a <= @b AND @a = @a - ( ABS(@a-@b) + (@a-@b) ) / 2)
	    	OR (@a >= @b AND @a = @a + ( ABS(@b-@a) + (@b-@a) ) / 2)
		    THEN 'Success' ELSE 'Failure' END AS Status
	END

Although the jump from scottyc's MIN function to the MAX function should have been obvious to me, it wasn't, so I've solved for it and included it here: SELECT @a + ( ABS(@b-@a) + (@b-@a) ) / 2. The randomly generated numbers, while not proof, should at least convince skeptics that both formulae are correct.

Select MIN(T.V) FROM (Select 1 as V UNION Select 2 as V) T