Question

I can certainly do this by iterating through results with PHP, but just wanted to know if someone had a second to post a better solution.

The scenario is that I have a list of transactions. I select two dates and run a report to get the transactions between those two dates…easy. For one of the reporting sections though, I need to only return the transaction if it was their first transaction.

Here was where I got with the query:

 SELECT *, MIN(bb_transactions.trans_tran_date) AS temp_first_time 
 FROM 
   bb_business      
   RIGHT JOIN bb_transactions ON bb_transactions.trans_store_id = bb_business.store_id 
   LEFT JOIN bb_member ON bb_member.member_id = bb_transactions.trans_member_id 
 WHERE 
   bb_transactions.trans_tran_date BETWEEN '2010-08-01' AND '2010-09-13' 
   AND bb_business.id = '5651' 
 GROUP BY bb_member.member_id 
 ORDER BY bb_member.member_id DESC

This gives me the MIN of the transactions between the selected dates. What I really need is the overall MIN if it falls between the two dates. Does that make sense?

I basically need to know if a customers purchased for the first time in the reporting period.

Anyways, no huge rush as I can solve with PHP. Mostly for my own curiosity and learning.

Thanks for spreading the knowledge!

EDIT:
I had to edit the query because I had left one of my trial-errors in there. I had also tried to use the temporary column created from MIN as the selector between the two dates. That returned an error.

SOLUTION:
Here is the revised query after help from you guys:

SELECT * FROM (
  SELECT 
    bb_member.member_id, 
    MIN(bb_transactions.trans_tran_date) AS first_time
  FROM 
    bb_business 
    RIGHT JOIN bb_transactions ON bb_transactions.trans_store_id = bb_business.store_id 
    LEFT JOIN bb_member ON bb_member.member_id = bb_transactions.trans_member_id 
  WHERE bb_business.id = '5651' 
  GROUP BY bb_member.member_id
) AS T 
WHERE T.first_time BETWEEN '2010-08-01' AND '2010-09-13'

Answer 1

If we do a minimum of all transactions by customer, then check to see if that is in the correct period we get something along the lines of…

This will simply give you a yes/no flag as to whether the customer’s first purchase was within the period…

SELECT CASE COUNT(*) WHEN 0 THEN 'Yes' ELSE 'No' END As [WasFirstTransInThisPeriod?]
FROM (  
        SELECT bb_member.member_id As [member_id], MIN(bb_transactions.trans_tran_date) AS temp_first_time 
        FROM bb_business      
        RIGHT JOIN bb_transactions ON bb_transactions.trans_store_id = bb_business.store_id 
        LEFT JOIN bb_member ON bb_member.member_id = bb_transactions.trans_member_id 
        WHERE bb_business.id = '5651' 
        GROUP BY bb_member.member_id
    ) T
WHERE T.temp_first_time BETWEEN '2010-08-01' AND '2010-09-13'
ORDER BY T.member_id DESC

(this is in T-SQL, but should hopefully give an idea of how this can be achieved similarly in mySQL)

Simon