Query syntax

Using MS SQL 2008.

I have a table (see below) that has the cumulative values for Diagnosed and Completed for each year.

I need to update the CumulativeActive column by subtracting the CumulativeCompleted from the previous year from the CumulativeDiagnosed of the current year.  

The table should look like this.  The one exception is the first year as then there is no previous year so you can do the subtraction.

yr      CumulativeDiagnosed   CumulativeActive   CumulativeCompleted
2010     4                                    0                                1
2011    16                                   0                                2
2012    27                                   0                                2
2013    40                                   0                                3
2014    121                                 0                                8

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so the table should look like this:

yr      CumulativeDiagnosed   CumulativeActive   CumulativeCompleted
2010     4                                    4                               1
2011    16                                   15                             2
2012    27                                   25                             2
2013    40                                   38                             3
2014    121                                 118                           8

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Can anyone help me with the script?

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are those the only columns in that table ?
What is the primary key of that table ?
Scott PletcherSenior DBACommented:
UPDATE curr_yr
SET  CumulativeActive =  curr_yr.CumulativeDiagnosed -
    ISNULL(prev_yr.CumulativeCompleted, 0)
FROM table_name curr_yr
LEFT OUTER JOIN table_name prev_yr ON
    prev_yr.yr = curr_yr.yr - 1

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soozhCEOAuthor Commented:
Thanks that is perfect.  I was struggeling with a solution that ordered the rows and did not Think i could just join on the current and previous year.  Also neat way to handle the first record with the isnull.

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Microsoft SQL Server

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