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SQL select sum() ...ignoring null's

Posted on 2003-10-28
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Last Modified: 2012-06-21
i have a table test1 (a int)
there are following values:
1
2
3
4
null

now i want select the sum of the column a, i do:
select sum(case when a is null then 0 end) from test1

should be 10 ..but it doesnt run how i specified. i want that the null is ignored. how do i do that?

also i want calculate the average of the table above. there are 4 times a value set, (1+2+3+4) / 4 = 2.5

thx a lot
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Question by:soci28
7 Comments
 

Assisted Solution

by:AndrewKT
AndrewKT earned 50 total points
ID: 9633713
Your logic is missing a small item:

create table #test (a int null)

insert into #Test values (1)
insert into #Test values (2)
insert into #Test values (3)
insert into #Test values (4)
insert into #Test values (null)

select sum(case when a is null then 0 else a end) from #test


You gave the sum function a value only when a is null.
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Assisted Solution

by:Lowfatspread
Lowfatspread earned 50 total points
ID: 9633717
you don't need the case

select sum(a.int),avg(a.int)


will ignore the null values  in the columns from the calculations automatically..
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LVL 18

Accepted Solution

by:
ShogunWade earned 25 total points
ID: 9633718
SELECT avg(a),sum(a) from test1
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LVL 18

Expert Comment

by:ShogunWade
ID: 9633727
Pipped at the post again by lowfat ;)
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Author Comment

by:soci28
ID: 9633869
is there a way to find out the average, if the table has more columns than one?

table test1 (a int, b int, c int, d int)
a  b  c  d
2  4  9  null

==> average should be 5 .. how do i find that?
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LVL 18

Expert Comment

by:ShogunWade
ID: 9633948
select (isnull(a,0)+isnull(b,0)+isnull(c,0)+isnull(d,0)) /
         ( case when a is null 0 else 1 end+case when b is null 0 else 1 end+case when c is null 0 else 1 end+case when d is null 0 else 1 end)
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Expert Comment

by:Lowfatspread
ID: 9639082
shogun's solution is the only way for sql server although i believe oracle has
function which work "on" a row..
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