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computed column - DataPresent

Posted on 2013-06-13
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Last Modified: 2013-06-17
I would like to put a "1" in the DataPresent column if the Total column is greater than 0

SELECT Month, Total, CASE WHEN TOTAL > 0 THEN 1 END AS DataPresent FROM AttendanceGrid

How can I make a computed column and have it automatically do that when a record changes in SQL?
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Question by:al4629740
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7 Comments
 
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Expert Comment

by:BAKADY
ID: 39245061
what do you mean with :  ... ?
How can I make a computed column and have it automatically do that when a record changes in SQL?
do you mean at vb6 at program level???
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Expert Comment

by:Aneesh Retnakaran
ID: 39245068
that seems to be almost perfect except the missng else part

SELECT Month, Total, CASE WHEN TOTAL > 0 THEN 1 ELSE 0 END AS DataPresent FROM AttendanceGrid
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Author Comment

by:al4629740
ID: 39245084
I mean have the record produce a "1" in the DataPresent field anytime the Total > 0 for that record.

This would happen in the SQL table.  I would like to enter the SQL statement as a computed column so that it automatically occurs

So if Total > 0 Then Datapresent = 1
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Accepted Solution

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Aneesh Retnakaran earned 350 total points
ID: 39245119
ALter table AttendanceGrid  add DataPresent  as CASE WHEN TOTAL > 0 THEN 1 ELSE 0 END
that will create the computed column, but i prefer a persisted computed column

refer this link

http://www.mssqltips.com/sqlservertip/1682/using-computed-columns-in-sql-server-with-persisted-values/
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Expert Comment

by:BAKADY
ID: 39245140
aneeshattingal was faster and he is right

ID: 39245119

after that you will be able to call your data with this

SELECT Month, Total, DataPresent FROM AttendanceGrid

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Assisted Solution

by:Scott Pletcher
Scott Pletcher earned 150 total points
ID: 39245258
Since the value can be only 1 or 0, I'd explicitly make the data type a bit:


ALTER TABLE dbo.AttendanceGrid
    ADD DataPresent AS CAST(CASE WHEN total > 0 THEN 1 ELSE 0 END AS bit)
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Expert Comment

by:PortletPaul
ID: 39246451
This computed column relates also to question: Find Starting Month of Activity

@al4629740
please note, this computed column does not assist in the determination of "first month"
all it does is indicate "TOTAL > 0" (or not)

to be honest I think this computed column may be a redundancy - but you may have other purposes for it that I'm unaware of.
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