//创建表DROP TABLE IF EXISTS updatelog;CREATE TABLE `updatelog` (  `id` int(11) NOT NULL AUTO_INCREMENT,  `resourceid` int(11) DEFAULT NULL,  `log` text,  `createtime` datetime DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=MyISAM DEFAULT CHARSET=latin1//必须指定主键或unique，不然无法replaceDROP TABLE IF EXISTS reslastlog;CREATE TABLE `reslastlog` (  `resourceid` int(11) NOT NULL DEFAULT ‘0‘,  `log` text,  `updatetime` datetime DEFAULT NULL,  PRIMARY KEY (`resourceid`)) ENGINE=MyISAM DEFAULT CHARSET=latin1//创建触发器DROP TRIGGER IF EXISTS t_afterinsert_on_updatelog;delimiter //CREATE TRIGGER t_afterinsert_on_updatelogAFTER INSERT ON updatelogFOR EACH ROWBEGIN     replace into reslastlog(resourceid,log,updatetime) values(new.resourceid, new.log, new.createtime);END;//delimiter ; DROP TRIGGER IF EXISTS t_afterdelete_on_updatelog;delimiter //CREATE TRIGGER t_afterdelete_on_updatelogAFTER DELETE ON updatelogFOR EACH ROWBEGIN     delete from reslastlog where resourceid=old.resourceid;END;//delimiter ; //测试insert into updatelog(resourceid, log, createtime) values(1, "version 1-0",now());insert into updatelog(resourceid, log, createtime) values(1, "version 1-1",now());insert into updatelog(resourceid, log, createtime) values(2, "version 2-2",now());delete from updatelog where resourceid = 2;//触发器相关操作mysql> show triggers;+----------------------------+--------+-----------+--------------------------------------------------------------------------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+| Trigger                    | Event  | Table     | Statement                                                                                                          | Timing | Created | sql_mode | Definer        | character_set_client | collation_connection | Database Collation |+----------------------------+--------+-----------+--------------------------------------------------------------------------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+| t_afterinsert_on_updatelog | INSERT | updatelog | BEGIN     replace into reslastlog(resourceid,log,updatetime) values(new.resourceid, new.log, new.createtime);END | AFTER  | NULL    |          | root@localhost | latin1               | latin1_swedish_ci    | latin1_swedish_ci  || t_afterdelete_on_updatelog | DELETE | updatelog | BEGIN     delete from reslastlog where resouceid=old.resourceid;END                                              | AFTER  | NULL    |          | root@localhost | latin1               | latin1_swedish_ci    | latin1_swedish_ci  |+----------------------------+--------+-----------+--------------------------------------------------------------------------------------------------------------------+--------+---------+----------+----------------+----------------------+----------------------+--------------------+2 rows in set (0.00 sec)drop trigger t_afterinsert_on_updatelog;

//用户定义函数//创建资源基本信息表CREATE TABLE `baseinfo` (  `id` int(11) DEFAULT NULL,  `content` text) ENGINE=MyISAM DEFAULT CHARSET=latin1;insert into baseinfo values(1,"one");insert into baseinfo values(2,"two");insert into baseinfo values(3,"three");//创建每日资源pv表CREATE TABLE `dayinfo` (  `id` int(11) DEFAULT NULL,  `pv` int(11) DEFAULT NULL,  `day` date DEFAULT NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1;insert into dayinfo values(1,10,"2014-10-01");insert into dayinfo values(1,12,"2014-10-02");insert into dayinfo values(1,16,"2014-10-03");insert into dayinfo values(2, 30, "2014-10-02");查询资源指定时段降序排列mysql> select baseinfo.id as id, content, sum(pv) as totalpv from baseinfo,dayinfo where baseinfo.id=dayinfo.id and day>="2014-10-02" and day<="2014-10-03" group by id order by totalpv desc;+------+---------+---------+| id   | content | totalpv |+------+---------+---------+|    2 | two     |      30 ||    1 | one     |      28 |+------+---------+---------+上面的sql语法非常复杂，如果用UDF会方便简洁很多。1，查看用户定义函数功能是否开启，ON为开启show variables like ‘%func%‘;2，如果是OFF，则执行下面的操作set global log_bin_trust_function_creators=1;3，创建用户定义函数delimiter $$CREATE FUNCTION getTotalPV(targetid int,dayfrom date,dayto date) RETURNS intbegindeclare totalpv int default 0;set totalpv=(select sum(pv) from dayinfo where id = targetid and day>=dayfrom and day<=dayto);if totalpv is null then    set totalpv = 0;end if;return totalpv;end$$delimiter ;mysql> select id, content, getTotalPV(id, "2014-10-02", "2014-10-03") as totalpv from baseinfo order by totalpv desc;+------+---------+---------+| id   | content | totalpv |+------+---------+---------+|    2 | two     |      30 ||    1 | one     |      28 ||    3 | three   |       0 |+------+---------+---------+4，查看udf定义show create function getTotalPV;//存储过程drop procedure if exists getjson;delimiter $$create procedure getjson(   str1 varchar(1024),   str2 varchar(1024),   str3 varchar(1024),   str4 varchar(1024))begin   if str1 is NULL then       set str1="";   end if;   if str2 is NULL then       set str2="";   end if;   if str3 is NULL then       set str3="";   end if;   if str4 is NULL then       set str4="";   end if;   select CONCAT("[",str1,",",str2,",",str3,",",str4,"]") as jsonstr;end;$$delimiter ;mysql> call getjson("a","b","c","d");+-----------+| jsonstr   |+-----------+| [a,b,c,d] |+-----------+1 row in set (0.00 sec)

1.lib_mysqludf_sys简介mysql中没有执行外部命令的函数，要调用外部的命令，可以通过开发MySQL UDF来实现，lib_mysqludf_sys 就是一个实现了此功能的UDF库。下载地址：https://github.com/mysqludf/lib_mysqludf_sys2.使用方法2.1 安装部署(需要安装mysql-devel)a) lib_mysqludf_sys.so复制到mysql/lib/plugin目录下。b) 在mysql中创建函数(根据需要选取)：Drop FUNCTION IF EXISTS lib_mysqludf_sys_info;Drop FUNCTION IF EXISTS sys_get;Drop FUNCTION IF EXISTS sys_set;Drop FUNCTION IF EXISTS sys_exec;Drop FUNCTION IF EXISTS sys_eval; Create FUNCTION lib_mysqludf_sys_info RETURNS string SONAME ‘lib_mysqludf_sys.so‘;Create FUNCTION sys_get RETURNS string SONAME ‘lib_mysqludf_sys.so‘;Create FUNCTION sys_set RETURNS int SONAME ‘lib_mysqludf_sys.so‘;Create FUNCTION sys_exec RETURNS int SONAME ‘lib_mysqludf_sys.so‘;Create FUNCTION sys_eval RETURNS string SONAME ‘lib_mysqludf_sys.so‘;2.2 使用此函数例：在select语句调用mkdir命令Select sys_exec(‘mkdir -p /home/user1/aaa‘)例：在触发器中调用外部的脚本(脚本需要可执行权限)Create TRIGGER trig_test AFTER Insert ON <table1>FOR EACH ROW BEGIN    DECLARE ret INT;    Select sys_exec(‘/home/user1/test.sh‘) INTO ret;END