DB noob here.

I have a table named invoice with a m:m relationship with a few other tables via junction tables:

  • invoice_customer
  • invoice_creator
  • invoice_deposit
  • invoice_withdrawal
  • invoice_payment_method

I'm trying to execute a query that will LEFT JOIN all of the data of these m:m relationships, however, seemingly at random, I'm getting duplicate results. Sometimes it gives the right amount, then when some state is modified it will give duplicates, and I can't seem to figure out why.

For example, this query gives me a result of "1" given I have one record matching the query:

FROM invoice
JOIN account_invoice
    ON account_invoice.account_id = ?
    AND account_invoice.invoice_id = invoice.id
WHERE invoice.deleted_at IS NULL

But this query gives me 4 duplicate records instead of 1:

SELECT invoice.*, account.*, customer.*, payment_method.*, deposit.*, withdrawal.*
FROM invoice
LEFT JOIN account_invoice
    ON account_invoice.invoice_id = invoice.id
LEFT JOIN account
    ON account.id = account_invoice.account_id
LEFT JOIN invoice_customer
    ON invoice_customer.invoice_id = invoice.id
LEFT JOIN customer
    ON customer.id = invoice_customer.customer_id
LEFT JOIN invoice_payment_method
    ON invoice_payment_method.invoice_id = invoice.id
LEFT JOIN payment_method
    ON payment_method.id = invoice_payment_method.payment_method_id
LEFT JOIN invoice_deposit
    ON invoice.id = invoice_deposit.invoice_id
LEFT JOIN transaction AS deposit
    ON deposit.id = invoice_deposit.transaction_id
LEFT JOIN invoice_withdrawal
    ON invoice.id = invoice_withdrawal.invoice_id
LEFT JOIN transaction AS withdrawal
    ON withdrawal.id = invoice_withdrawal.transaction_id
WHERE account.id = ?
    AND invoice.deleted_at IS NULL
ORDER BY invoice.id DESC
  • 1
    They are not really duplicates. If you have an invoice related with 2 deposits and 2 withdrawals, your query will rightfully return 4 rows. That's what you asked for. Dec 22, 2018 at 10:29
  • 1
    If there are also 3 related payment methods the result will be 12 rows. One for each combination of related deposits, withdrawals and payment methods. Dec 22, 2018 at 10:31
  • It seems like payment_method would be tied to deposit and to withdrawal??
    – Rick James
    Dec 22, 2018 at 16:27
  • @RickJames Yes it's used for the withdrawal mostly, but I just attach it to the invoice for now.
    – Lansana
    Dec 22, 2018 at 16:31
  • @yper-crazyhat-cubeᵀᴹ Good point, however there is only one result in each of the junction tables.
    – Lansana
    Dec 22, 2018 at 16:32

1 Answer 1


If you want only one row of output for each Invoice, you need to figure out what to do with multiple customers tied to that one invoice. (Etc.) Here's one approach:

           ( SELECT c.name FROM invoice_customers AS ic
                           JOIN customers AS c  USING(customer_id)
                           WHERE ic.invoice_id = i.invoice_id
           ) SEPARATOR ", "
                   ) AS customers
    FROM invoices AS i

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