SQL Server 2008中的滞后功能

Question

I`m writing on SQL Server 2012 in this SQL function

;With Quote as 
(
    SELECT 
        SID, SHEET, Code, Date, Data, 
        LAG(Data) OVER(ORDER BY Date) As LastMonthData 
    FROM 
        RMQ_DATA 
    WHERE 
        [SHEET] IN ('0', '1')
)
SELECT 
    [Quote].[SID], Quote.DATE, Quote.DATA, Quote.SHEET, Quote.CODE,
    CASE 
       WHEN ISNULL(LastMonthData, 0) = 0 THEN null 
       ELSE (Data-LastMonthData)/LastMonthData
    END As Quote
FROM 
    Quote
Left outer Join 
    RMQ_SUBCAT on  Quote.CODE =RMQ_SUBCAT.TARGET_CODE
left outer join 
    RMQ_CAT on RMQ_SUBCAT.TARGET_SID=RMQ_CAT.SID
where 
    RMQ_CAT.ENABLED='Y' and 
    Quote.DATE between '2014/01/01' and '2016/12/01'

but on the first line

;With Quote as (
SELECT SID,SHEET,Code, Date, Data, 
       LAG(Data) OVER(ORDER BY Date) As LastMonthData 
       FROM RMQ_DATA WHERE [SHEET] IN('0','1'))

LAG(Data) I have an error. So I don't know LAG() function how to use in SQL Server 2008.

How can I solve this trouble ?

Answer 1

If you can't execute this in SQL Server 2012 meaning you can't use LAG function, AND you know that the "Date" data doesn't have ANY gaps, then a workaround is to self-join the same table.

for eg, instead of this

SELECT 
    SID, SHEET, Code, Date, Data, 
    LAG(Data) OVER(ORDER BY Date) As LastMonthData 
FROM 
    RMQ_DATA 
WHERE 
    [SHEET] IN ('0', '1')

use something like this

select A.SID, A.SHEET, A.Code, A.Date, A.Data as ThisMonthData, B.Data as LastMonthData from RMQ_DATA A, RMQ_DATA B where A.sid= B.sid and A.sheet=B.sheet and A.date=add_months(B.Date,1) where [SHEET] IN ('0', '1')

add_months is an Oracle function, and might not be right for your dates anyway, but you get the idea.

If the Date data has any gap in it, then this won't work, you will miss rows - you'd need to join some kind of row generator to make this work. It gets ugly fast, as marc_s said.