How do I conditionally select a field from one of two tables?

Posted by freakwincy on Stack Overflow See other posts from Stack Overflow or by freakwincy
Published on 2010-04-15T14:10:19Z Indexed on 2010/04/15 14:13 UTC
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mysql

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select

I have two tables invoices and pending_payments both of which have the following rows in common: invoice_id and balance. I want to do a select in MySQL that'll work thus:

[pseudo-code]

if(invoice_id exists in pending_payments table) {
    select balance from pending_payments where invoice_id = yadayadayada
} else {
    select balance from invoices where invoice_id = yadayadayada
}

Is this even doable in MySQL? If so, how?

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