SQL Server：使用参数代替GETDATE（）

Question

I have a stored procedure that uses selects like the following which works fine so far. In this case for example it selects all records with a date from the previous month, ie March 2014 (column: dateEsc, formatted as nvarchar(20) , example date: 2014-03-25).

My Select (example):

SELECT COUNT(*) AS groupCount
FROM Log_Esc
WHERE 
    CONVERT(DATE, dateEsc, 120) >= CONVERT(DATE, CONVERT(VARCHAR(6), DATEADD(month, -1, GETDATE()), 112) + '01', 112)

How do I have to change this if instead of the current Date (GETDATE()) I want to use a variable date input as the reference. This input would be any date and is formatted as nvarchar(20) as well, example: 2014-04-03.

So instead of calculating the previous month compared to the current month from GETDATE() I would like to calculate the same from the variable date input.

Many thanks for any help with this, Tim.

Answer 1

First of all I think this query is better than the one you have:

SELECT COUNT(*) AS groupCount
FROM Log_Esc
WHERE DATE >= dateadd(month,datediff(month,0,dateadd(month,GETDATE(),-1)),0)
 AND  DATE <  dateadd(month,datediff(month,0,GETDATE()),0)

If there is an index on the DATE field this can do a seek.

If you have a parameter @indate defined as date or datetime then this will work

SELECT COUNT(*) AS groupCount
FROM Log_Esc
WHERE DATE >= dateadd(month,datediff(month,0,dateadd(month,@indate,-1)),0)
 AND  DATE <  dateadd(month,datediff(month,0,@indate),0)

See this question for more information on flooring a date to a month: Floor a date in SQL server

Answer 2

So what you want is a parameter:

Specifying Parameters in a Stored Procedure

Parameters allow you to pass user input to modify output.

An example

CREATE PROCEDURE dbo.Param1
@param int 
AS
BEGIN

select 7 *@param as Value
END

EXEC dbo.Param1 5 -- 7 *5
EXEC dbo.Param1 -10  -- 7 * -10

Perhaps this'll give you some creative ideas for how you might implement parameters to accomplish your group count.