一个复杂的mysql查询语句(case,when,then,left join )
select `a`.`id` AS `id`,`a`.`UserName` AS `UserName`,
(case when (`a`.`sRegDate` = _utf8'1990-01-01 00:00:00.0') then _utf8'' else cast(date_format(`a`.`sRegDate`,_utf8'%Y-%m-%d %H:%i:%S') as char charset utf8) end) AS `sRegDate`,(case when (`a`.`feeendtime` = _utf8'1990-01-01 00:00:00.0') then _utf8'' else cast(date_format(`a`.`feeendtime`,_utf8'%Y-%m-%d %H:%i:%S') as char charset utf8) end) AS `feeendtime`,
(case when (`a`.`iStatus` = _utf8'0') then _utf8'正常' when (`a`.`iStatus` = _utf8'1') then _utf8'锁定' when (`a`.`iStatus` = _utf8'2') then _utf8'欠费' when (`a`.`iStatus` = _utf8'') then _utf8'申请停机' else _utf8'' end) AS `iStatus`,
(case when (`a`.`PayType` = _utf8'0') then _utf8'免费' when (`a`.`PayType` = _utf8'2') then _utf8'小区网用户' when (`a`.`PayType` = _utf8'10') then _utf8'外部用户' else _utf8'' end) AS `PayType`,
`c`.`UserType` AS `sDh1`,`b`.`FeeName` AS `iFeeType`,
(case when (`a`.`PauseStartTime` = _utf8'1990-01-01 00:00:00.0') then _utf8'' else cast(date_format(`a`.`PauseStartTime`,_utf8'%Y-%m-%d %H:%i:%S') as char charset utf8) end) AS `PauseStartTime`,
(case when (`a`.`PauseStopTime` = _utf8'1990-01-01 00:00:00.0') then _utf8'' else cast(date_format(`a`.`PauseStopTime`,_utf8'%Y-%m-%d %H:%i:%S') as char charset utf8) end) AS `PauseStopTime`,
(case when (`a`.`AcctStartTime` = _utf8'1990-01-01 00:00:00.0') then _utf8'' else cast(date_format(`a`.`AcctStartTime`,_utf8'%Y-%m-%d %H:%i:%S') as char charset utf8) end) AS `AcctStartTime`,
(case when (`a`.`AcctStopTime` = _utf8'1990-01-01 00:00:00.0') then _utf8'' else cast(date_format(`a`.`AcctStopTime`,_utf8'%Y-%m-%d %H:%i:%S') as char charset utf8) end) AS `AcctStopTime`,
`a`.`speed` AS `speed`,
(case when (`a`.`idtype` = _utf8'7') then _utf8'身份证' when (`a`.`idtype` = _utf8'1') then _utf8'教职工' when (`a`.`idtype` = _utf8'2') then _utf8'本科生' when (`a`.`idtype` = _utf8'3') then _utf8'研究生' when (`a`.`idtype` = _utf8'4') then _utf8'离退生' when (`a`.`idtype` = _utf8'5') then _utf8'
相关文档：
一直以为mysql随机查询几条数据，就用
SELECT
*
from
`
table
`
ORDER
BY
RAND
() LIMIT
5
就可以了。
但是真正测试一下才发现这样效率非常低。一个15万余条的库，查询5条数据，居然要8秒以上
查看官方手册，也说rand()放在ORDER BY 子句中会被执行� ......
给mysql开一个可以远程访问的用户命令如下:
GRANT ALL PRIVILEGES ON *.* TO 'myuser'@'%' IDENTIFIED BY 'mypassword' WITH GRANT OPTION;
"*.*" 表示数据库中所有的表,也可以换成指定的表如test.*
"myuser" 表示的是访问的用户名;
"%" 表示所有的主机即任何的主机都可以通过这个用户名访问我的数据库,也可以该成特定� ......
1. 给root加密码：/usr/bin/mysqladmin -u root password 123456
2. 导出：mysqldump -u root -p dbname > file.sql
3. 导入：mysql -u root -p dbname < backup-file.sql
4. 授权：grant all on *.* to root@"%" identified by "密码";
5. 收回权限：revoke all privileges on *.* from root@"%";
6. 登录：mys ......
Some problems encounted this afternoon, when trying to setup/test mysql capabilities on hypnos and virgil.
1.ERROR 2003 (HY000): Can't connect to MySQL server on 'server-name' (111)
access locally (i.e. from localhost) is fine, when trying remotely got this error. when tried with mysql++ library, ......
