using group_concat with other selection criteria - mySQL

Question

I have two tables, arrc_PurchActivity and arrc_Voucher. The purchase activity table contains multiple records per purchase, tied together by the credit card authorization. I need to return a single row per purchase, plus pull in a field from the voucher table. If I just grab a few fields from the purchase activity table, like this:

SELECT group_concat( VoucherID ) , CcAuthCode FROM arrc_PurchaseActivity GROUP BY CcAuthCode

it works fine, returning something like this:

group_concat( VoucherID )  | CcAuthCode
=========================================
610643,611139,610642       | 8LUPDN

What I need to do is pull in another contatenated field (VoucherNbr), this time from the arrc_Voucher table, where the voucher table's VoucherID is equal to the purchase table's VoucherID. In this case, because VoucherID is a concatenation, I need to return a concatenated column of VoucherNbr for each VoucherID in the concatenated column. Clear as mud, right? What I need would look like this:

group_concat( VoucherID )  | group_concat( VoucherNbr)  |  CcAuthCode
===========================|============================|=============
610643,611139,610642       | 123,456,789                |  8LUPDN 

In other words, the VoucherNbr for VoucherID 610643 is 123, VoucherNbr for 611139 is 456, etc.

Can anyone help me out? This is way over my head...

Answer 1

Use:

   SELECT pa.ccauthcode,
          GROUP_CONCAT(DISTINCT pa.voucherid) AS voucherids,
          GROUP_CONCAT(v.vouchernbr) AS vouchernbrs
     FROM ARRC_PURCHASEACTIVITY pa 
LEFT JOIN ARRC_VOUCHER v ON v.voucherid = pa.voucherid
 GROUP BY pa.ccauthcode

I specified the DISTINCT in the GROUP_CONCAT for the voucherid's because it's possible you'd have multiple vouchernbr's to a voucherid. If not, remove the DISTINCT.

The LEFT JOIN ensures you'll get ARRC_PURCHASEACTIVITY records that do not have supporting records in ARRC_VOUCHER. Change "LEFT JOIN" to "JOIN" if you don't want this behavior.