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� ......
/*演示一个JDBC程序，从Mysql的LMD数据库中读出表admin的一个信息*/
import java.sql.*;
public class TestMysqlConnection {
public static void main(String[] args) {
Connection conn = null;
Statement stmt = ......
用mysql_query，mysql_fetch_array()后应该要
free_result().function count_admin($where = '')
{
if($where) $where = " WHERE $where";
$result = $this->db->get_one("SELECT count(*) as num from $this->table_admin_role $where");
return $result['num'];
} ......
MySQL数据库备份和还原的常用命令
原文见http://www.21andy.com/blog/20071102/655.html
时间：2007-11-02 23:29:09 类别：技术 访问：3,731 views RSS 2.0 评论
备份MySQL数据库的命令
mysqldump -hhostname -uusername -ppassword database ......
