CODEWITHSUNDEEP
sqlsql-serversql-server-2008-r2
Waller
Waller

Reputation: 1873

Calculating based on the above row SQL

I am trying to work out what the previous months invoice value was, and put it on the same row as the current value.

I'm using SQL Server.Microsoft SQL Server 2008 R2 (SP2)

I've tried my luck using CTE's and all kind of weird joins, but my output is never correct. Can someone point me in the correct direction?

Example table:

invoice_month   value
--------------------------
    201510      337265.386
    201511      335466.456
    201512      338646.500
    201601      333440.380
    201602      330731.208
    201603      339299.752
    201604      340878.168
    201605      359585.382
    201606      339616.430
    201607      316457.486
    201608      308009.976
    201609      232196.268
    201610      894839.180
    201611      232196.268
    201612      232196.268
    201701      232196.268
    201702      232196.268
    201703      232196.268

Expected output would be:

invoice_month   value,         prevValue
--------------------------------------------
    201510      337265.386,    NULL
    201511      335466.456,    337265.386
    201512      338646.500,    335466.456
    201601      333440.380,    333440.380
    201602      330731.208,    333440.380
    201603      339299.752,    330731.208
    201604      340878.168,    339299.752
    201605      359585.382,    340878.168
    201606      339616.430,    359585.382
    201607      316457.486,    339616.430
    201608      308009.976,    316457.486
    201609      232196.268,    308009.976
    201610      894839.180,    232196.268
    201611      232196.268,    894839.180
    201612      232196.268,    232196.268
    201701      232196.268,    232196.268
    201702      232196.268,    232196.268
    201703      232196.268,    232196.268

Upvotes: 3

Views: 81

Answers (3)

user2173966
user2173966

Reputation: 136

SELECT *
FROM   (SELECT TOP 1 invoice_month,
                     value,
                     NULL AS [Previous value]
        FROM   Invoice
        ORDER  BY invoice_month ASC) T
UNION
SELECT I.invoice_month,
       I.value,
       I1.value AS [Previous value]
FROM   Invoice I
       INNER JOIN Invoice I1
               ON I.invoice_month - 1 = I1.invoice_month

Upvotes: 0

TheGameiswar
TheGameiswar

Reputation: 28900

for versions prior to 2012: 

;with cte
 as
(select invoice_month,value,
row_number() over (order by invoice_month) as rn
from  #temp  )
select c1.*,c2.value
from cte c1
left join
cte c2
on c1.rn=c2.rn+1

Upvotes: 3

Gordon Linoff
Gordon Linoff

Reputation: 1269753

In SQL Server 2012+, you would use lag():

select t.invoice_month, t.value,
       lag(t.value) over (order by t.invoice_month) as prev_value
from t;

This is an ANSI standard function. In earlier versions of SQL Server, there are alternative methods.

Upvotes: 4

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