修改某一条数据时,如果数据没有任何修改,提交后,由于提交的内容与原内容相同,所以$this->ezsql->query($sql)的结果返回的是0。如果提交的内容字段与原字段不符,那么更新成功 ,则返回的结果为1。由于更新数据,$this->ezsql->query($sql) 返回的结果为影响的记录数。查看源码得知,实际获取该结果的是通过:mysql_...
mysql做update时有in关联子查询条件时效率奇慢分析 # Query_time: 4.568689 Lock_time: 0.000068 Rows_sent: 0 Rows_examined: 6157476 SET timestamp=1414501476; UPDATE push_group_task SET arrive_num = arrive_num+1,update_time = NOW() WHERE id IN (SELECT p.group_task_id FROM push_task p WHERE...
SQL UPDATE 语句: mysql>UPDATErunoob_tblSETrunoob_title='学习 C++'WHERErunoob_id=3;QueryOK,1rowsaffected(0.01sec)mysql>SELECT*fromrunoob_tblWHERErunoob_id=3; +---+---+---+---+ |runoob_id|runoob_title|runoob_author|submission_date| +---+---+---+---+ |3| 学习C++ |RUNOOB.COM|2...
Re: Eliminate filesort in update query 1071 Rick James October 03, 2014 10:09PM Re: Eliminate filesort in update query 1111 Matzz - October 04, 2014 03:13AM Sorry, you can't reply to this topic. It has been closed. Content reproduced on this site is the property of the respective ...
cursor.execute(select_query)执行查询语句。 cursor.fetchall()获取查询结果。 for row in result: print(row)打印查询结果。 总结 通过以上步骤,我们可以使用UPDATE语句根据查询结果修改对应记录的某个字段。首先,我们需要连接到MySQL数据库;然后,编写UPDATE语句,并执行它;接着,提交更改以保存修改;最后,可以通过查询...
ha_innobase::update_row: row_get_prebuilt_update_vector calc_row_difference row_update_for_mysql row_upd_step row_upd --执行更新 btr_pcur_t::restore_position rec_get_offsets_func btr_cur_update_in_place btr_cur_upd_lock_and_undo trx_undo_report_row_operation trx_undo_create trx_undo...
mysql> update teachersetname='ccc'order by id desc limit2; Query OK,2rows affected (0.06sec) Rows matched:2Changed:2Warnings:0mysql>select*fromteacher;+---+---+---+ | id | name | dept_id | +---+---+---+ |10002| bbb |1| |10003| ccc |4| ...
Error Code: 1093. You can't specify target table 'sys_user' for update in FROM clause0.000 sec 原因: mysql中不支持子查询更新,准确的说是更新的表不能在set和where中用于子查询。那串英文错误提示就是说,不能先select出同一表中的某些值,再update这个表(在同一语句中)。
7 rows in set mysql> UPDATE employees INNER JOIN merits ON employees.performance = merits.performance SET salary = salary + salary * percentage; -- 执行连接更新 Query OK, 6 rows affected Rows matched: 7 Changed: 6 Warnings: 0 mysql> select * from employees; -- 更新之后的数据 ...
在MySQL和PostgreSQL中,可以使用exec_query或exec_update来执行查询和更新操作。 1. MySQL中使用exec_query或exec_update: - ex...