Grouping and looping in a stored procedure

Question

I need to do a sum on the columns MTH1 MTH2 etc but for the parameters I pass it will produce six rows of information for the same account code which is correct and what it shou

Answer 1

You seem to simply want a GROUP BY. But you can also simplify the query in other ways:

select nl.ACCOUNT_REF, 
    sum(nl.PRIOR_YR_MTH1) as PRIOR_YR_MTH1,
    sum(nl.PRIOR_YR_MTH2) as PRIOR_YR_MTH2,
    . . .  - fill in the rest of the months
from NOMINAL_LEDGER nl join         
     CATEGORY c
     on c.CompanyID = nl.CompanyID
where nl.ACCOUNT_REF = @AccountRef and
      nl.SORT_ORDER = @SortOrder and
      c.CATEGORY = @CATEGORY
group by nl.ACCOUNT_REF;

Notes:

• The WHERE clause (presumably) undoes the LEFT JOIN, turning it into an INNER JOIN. So use the proper JOIN.
• Table aliases make the query easer to write and to read.
• You seem to want one row per account, so the query aggregates by account and leaves out the other non-aggregated columns.