Question

I want to [update] the transaction_id from transactions table into the cmas table but I’m missing something… not sure where to reference the cmas table so it doesn’t error #1054 - Unknown column 'cmas.property_id' in 'where clause'

INSERT INTO `cmas` (`transaction_id`)
SELECT `transaction_id`
FROM `transactions` WHERE transactions.property_id = cmas.property_id // this bit is wrong!

Answer 1

Since you mention updates in the comments, this might be what you are looking for:

UPDATE cmas, transactions
SET cmas.transaction_id = transactions.transaction_id
WHERE transactions.property_id = cmas.property_id