Question

I have a SQL query where in I have to fetch an additional param from a different table, only if a value is present in the primary table. I have tried using the if else clause, but it never works.

The SQL looks like this:

SELECT  
   hist.I_PAYT_REF AS PAY_REF,
   hist.C_USERID AS USER_ID,
   IF(@hist.I_PAYT_REF IS NULL)
   BEGIN
      SELECT 
         PAYT.I_PAYT_REQ_SUM AS PAYMENT_FILE_ID
      Join 
         SP.TSP_CP_PAYT_RQ_DTL PAYT ON PAYT.I_PAYT_REF = hist.I_PAYT_REF
   END
FROM 
   sp.TSP_CP_HIST hist
WHERE 
   hist.C_HIST_TYPE ='V'

All I want to do is fetch a a new parameter if the hist.I_PAYT_REF is not null. Any help will be greatly appreciated.

Thanks,
Yeshwanth

Answer 1

You just need a left join, if I_PAYT_REF is null the join will not exclude the main hist record and PAYMENT_FILE_ID will be returned null anyway.

SELECT  
    hist.I_PAYT_REF AS PAY_REF,
    hist.C_USERID AS USER_ID,
    PAYT.I_PAYT_REQ_SUM AS PAYMENT_FILE_ID
    FROM 
         SP.TSP_CP_HIST hist left join 
         SP.TSP_CP_PAYT_RQ_DTL PAYT ON PAYT.I_PAYT_REF = hist.I_PAYT_REF 
    WHERE hist.C_HIST_TYPE ='V'