SQL 更新语句报错：子查询返回多个结果的解决方案

UPDATE box_draw_record SET box_price = ( SELECT COALESCE ( price, 0 ) FROM box WHERE id = box_draw_record.box_id ) WHERE box_price = 0;

报错可能是因为子查询返回了多个结果，而 UPDATE 只能更新单个值。可以将子查询改为 JOIN，如下所示：

UPDATE box_draw_record JOIN box ON box.id = box_draw_record.box_id SET box_draw_record.box_price = COALESCE(box.price, 0) WHERE box_draw_record.box_price = 0;