MySQL Update a field value with subquery with multiple returning rows?

It's probably worthwhile to ensure that your UPDATE statement is trying to update each user's row exactly once. A subquery is the best way to do this, most efficiently implemented as a joined table.

It's probably worthwhile to ensure that your UPDATE statement is trying to update each user's row exactly once. A subquery is the best way to do this, most efficiently implemented as a joined table: UPDATE bank JOIN (SELECT LOWER(bonds. Holder) as user, SUM(bonds.

IssuePrice * bonds. Coupon) as total FROM bonds WHERE LOWER(bonds. Holder)!

= 'bank' GROUP BY user ) as increments ON increments. User = LOWER(bank. User) SET bank.

Cash = ROUND(bank. Cash + increments. Total, 2), bank.

Earned = ROUND(bank. Earned + increments. Total, 2) (For more optimization, the LOWER and ROUND calls should probably be eliminated, but that's another discussion.).

Thanks, this worked! – Gilles Lesire Dec 11 '10 at 12:17.

The most straighforward way is to use sub-selects and update the fields individually... UPDATE bank ba1 SET ba1. Cash = ba1. Cash + (ROUND(SELECT SUM(bo.

IssuePrice * bo. Coupon) FROM bank ba2 JOIN bonds bo ON bo. User = ba2.

User WHERE ba2. User = ba1. User), 2) ...

This worked too but I think the other query is easier and more performant. – Gilles Lesire Dec 11 '10 at 12:19.

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