查看 MySQL 服务器运行的各种状态值: mysql> show global status: 1. 慢查询 mysql> show variables like '%slow%'; +---------------------------+-------------------------------+ | Variable_name | Value | +---------------------------+-------------------------------+ | log_
DELIMITER $$ USE `local_hnyz`$$ DROP FUNCTION IF EXISTS `GET_ORDER_STATUS`$$ CREATE DEFINER=`root`@`localhost` FUNCTION `GET_ORDER_STATUS`(orderId VARCHAR(64)) RETURNS TINYINT-- varchar(64) CHARSET utf8BEGIN DECLARE seal_status VARCHAR(1) DEFAULT '';
子查询: 子查询,即嵌套在其他查询中的查询.例如我们有这样几个表,顾客表,订单表,商品表,我们想知道有哪些客户买了商品A,那么我们就需要先查看哪些订单里包含了商品A,然后根据订单查出是哪些客户. mysql> select cust_id from orders where order_num in (select order_num from orderitems where prod_id = '1'); +---------+ | cust_id | +---------+ | 10