Question

ID    M1      M2       M3    M4       DateM2        DateM3      DateM4 
1     2       NULL     NULL  NULL     NULL          NULL        NULL
2     NULL     2       1     1        11.11.2011    15.11.2011  20.11.2011
3     1       NULL     NULL  NULL     NULL          NULL        NULL
4     2       3        1     2        11.12.2012    12.12.2012  13.12.2012
5     1       1        1     1        11.10.2012    12.10.2012  13.10.2012
6     2       2        2     2        12.9.2012     12.12.2012  1.2.2013

i want to produce the following table which will have the ID column and a new Column

ID M1+M2+M3+M4
1  2
2  4
3  1
4  8
5  4
6  8

the new column will be M1+M2+M3+M4 with the following rules

1. M1 added always to the sum and if its null i set it to 0
2. M2 is added to the sum if DateM2 wasnt NULL AND DATE1 < DateM2 < DATE2
3. M3 is added to the sum if DateM3 wasnt NULL AND DATE1 < DateM3 < DATE2
4. M4 is added to the sum if DateM4 wasnt NULL AND DATE1 < DateM4 < DATE2

DATE1 and DATE2 are variables specified in the query, now my problem with this i am not sure what to use for the performance i have tens of thausands of records, should i use select case, you are welcome to help the way you can!

Answer 1

Something like this:

SELECT
t.ID,
isnull(t.M1,0)+
CASE WHEN t.DateM2 is not null AND @DATE1 < t.DateM2 < @DATE2
     THEN t.M2
     ELSE 0 END +
CASE WHEN t.DateM3 is not null AND @DATE1 < t.DateM3 < @DATE2
     THEN t.M3 
     ELSE 0 END +
CASE WHEN t.DateM4 is not null AND @DATE1 < t.DateM4 < @DATE2
     THEN t.M4 
     ELSE 0 END AS 'M1+M2+M3+M4'
FROM Table1 t