mysql query inner join on same table with different conditions

Question

I have a table transactions and I trying to figure out our new customers in a given month. That means that if a customer didn't have a transaction in the time before the month he/she counts as a new customer.

I have figured out a way, but it is seriously inefficient and takes ages. I then came across this artikel which compares different methods. I have tried to adjust that approach to mine without success.

To visualise my problem:

|--------------------------- time period with all transactions -----------------------|
|----- period before month transactions = 0) ---|---- curr month transactions > 0 ----|

The table looks like this:

transactions
id, email, state, date_paid

My query:

SELECT
    l.email
FROM
    transactions as l
LEFT JOIN transactions as r ON r.email = l.email
WHERE
    r.email IS NULL
AND l.state = 'paid'
AND r.state = 'paid'
AND l.date_paid <= '2013-12-31 23:59:59'
AND r.date_paid < '2013-12-01 00:00:00'

What am I doing wrong?

Answer 1

Try this:

SELECT l.email
FROM transactions AS l
LEFT JOIN transactions AS r ON r.email = l.email AND r.state = 'paid' AND r.date_paid < '2013-12-01 00:00:00'
WHERE r.email IS NULL AND l.state = 'paid' AND l.date_paid <= '2013-12-31 23:59:59'

Answer 2

try this:

SELECT l.email
FROM transactions l
WHERE NOT l.email IN (SELECT r.email 
                      FROM transactions r
                      WHERE r.state = 'paid' AND r.date_paid < '2013-12-01 00:00:00')
      AND l.state = 'paid' AND l.date_paid <= '2013-12-31 23:59:59'