Get the minimum value between several columns

Question

I\'m using SQL Server 2008;

Suppose I have a table \'X\' with columns \'Date1\', \'Date2\', \'Dateblah\', all of type DateTime.

I want to select the min valu

Answer 1

based on scalar function (from Tom Hunter):

SELECT ID, (SELECT MIN([date]) FROM (VALUES(Date1),(Date2),(Dateblah)) x([date])) MinDate
FROM TableName

Answer 2

Simply lets say the table where your dates are is called sells and it has two date fields Date1 and Date2 from which you want the minimum.

SELECT ( 
   SELECT MIN([x]) 
   FROM (VALUES(Date1),(Date2)) x([x])
) as minimum
FROM sells

Answer 3

Implementing a scalar function:

CREATE FUNCTION [dbo].[MIN](@a SQL_VARIANT, @b SQL_VARIANT)
RETURNS SQL_VARIANT
AS 
BEGIN
    RETURN (
        SELECT MIN([x])
        FROM (VALUES(@a),(@b)) x([x])
    )   
END
GO

DECLARE @a DATETIME = '12 JUL 2011', @b DATETIME = '20 AUG 2011'
SELECT [dbo].[MIN](@a, @b)

DECLARE @c INT = 12, @d INT = 32
SELECT [dbo].[MIN](@c, @d)

Answer 4

There is no built in function to return the min/max of two (or more) columns. You could implement your own scalar function to do this.

In SQL Server 2005+ you could use UNPIVOT to turn the columns into rows and then use the MIN function:

CREATE TABLE [X]
(
    [ID] INT,
    [Date1] DATETIME,
    [Date2] DATETIME,
    [Date3] DATETIME
)

INSERT  [X]
VALUES  (0, '09/29/2011', '09/20/2011', '09/01/2011'),
        (1, '01/01/2011', '01/05/2011', '03/03/2010')


SELECT [ID], MIN([Date]) AS [MinDate]
FROM [X]
UNPIVOT (
    [Date] FOR d IN
        ([Date1]
        ,[Date2]
        ,[Date3])
) unpvt
GROUP BY [ID]