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Case statement to sum values - T-SQL

Posted on 2016-10-13
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Last Modified: 2016-10-13
I'm trying to write a case statement  that sums up values, but the one below is producing null values. What am I doing wrong? *In a nutshell, (NL * 3%) + (DP * 1%) + (PR) = NR.

 sum((case
  when METRIC_CD = ''NL'' then
  MTD_ACT * 0.03 else null end) +
  (case when METRIC_CD = ''DP'' then
  MTD_ACT * 0.01 else null end) +
  (case when METRIC_CD = ''PR'' then
  MTD_ACT * 1 else null end)) as NR

Below is the data  as it appears in the table:

METRIC_CD      MTD_ACT
NL                       1200
DP                         500
PR                      3150
DP                      2250
PR                        550
NL                    11000


Thank you for your tremendous assistance.
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Question by:saved4use
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3 Comments
 
LVL 20

Accepted Solution

by:
Russ Suter earned 450 total points
ID: 41842669
Instead of else null use else 0 (that's zero).

Adding 0 won't affect your total but adding NULL will yield a NULL result. Take the following examples:

SELECT 1 + 3 + 0 + 5 => returns 9

SELECT 1 + 3 + NULL + 5 => returns NULL

The same holds true for the SUM() function. A NULL value in the aggregate will yield NULL.
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LVL 66

Assisted Solution

by:Jim Horn
Jim Horn earned 50 total points
ID: 41842678
Russ is correct, as NULL added to anything else will equal NULL.  And to make this a hell of a lot easier to read...
 SUM(CASE METRIC_CD 
   WHEN 'NL' THEN MTD_ACT * 0.03 
   WHEN 'DP' THEN MTD_ACT * 0.01 
   WHEN 'PR' THEN MTD_ACT * 1 ELSE 0 END) as NR

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Expert Comment

by:mbazar
ID: 41842969
Try this

sum((case
  when METRIC_CD = ''NL'' then MTD_ACT * 0.03
  when METRIC_CD = ''DP'' then MTD_ACT * 0.01
  when METRIC_CD = ''PR'' then MTD_ACT * 1
  else 0 end)) as NR
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