Method: ActiveRecord::ConnectionAdapters::DatabaseStatements#join_to_update

Defined in:
lib/active_record/connection_adapters/abstract/database_statements.rb

#join_to_update(update, select, key) ⇒ Object Also known as: join_to_delete

The default strategy for an UPDATE with joins is to use a subquery. This doesn’t work on MySQL (even when aliasing the tables), but MySQL allows using JOIN directly in an UPDATE statement, so in the MySQL adapters we redefine this to do that.



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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 355

def join_to_update(update, select, key) # :nodoc:
  subselect = subquery_for(key, select)

  update.where key.in(subselect)
end