批量更新一对多关系栏2.3.5一个sql语句？

Question

Lets say user has many accounts, so user_id is on accounts table. If I want to update all the users accounts and give them to another user in 1 sql call is there a "rails" way to do this? (without doing executeSQL)

So Joel has 1000 accounts, Fred has no accounts, Joel wants to give Fred all his accounts, normally I could iterate through joels accounts and assign them to fred user, but that would result in 1000 sql calls..

Answer 1

fred.accounts += joel.accounts

This will immediately move all accounts from joel and add them to any existing accounts that fred has. By "immediate" I mean the SQL will execute the update right away - you don't need to additionally save the records that are being moved.

If fred has no accounts, that's fine too, it still works the same - it will simply add joel 's accounts to fred 's empty list of accounts.

This works with both "one-to-many" and "many-to-many" relationship.

In the one-to-many situation, it does this my changing the user_id field on the accounts table for all accounts previously owned by joel .

In the many-to-many situation (where accounts can be co-owned by multiple users), it appears to simply change the user_id field on the join table (presumably called accounts_users ) for all accounts that joel co-owns with zero or more other users. This effectively replaces any accounts that joel co-owned with fred . All other co-owners on the account are unaffected, it seems.