设计需求。需要对后台数据定期做数据归档任务，把一张表的是数据在每天半夜将前n(可配置)天的数据进行归档，至于归档到哪一张表需要根据当天属于哪一个月来确定表的名字.

　　drop procedure if exists dataFile;

　　create procedure dataFile()

　　BEGIN

　　declare tableName varchar(100);

　　declare total int default 0 ;

　　declare intervalDay int default 7;

　　select pmt_val into intervalDay from postmail.dim_sys_pmt where pmt_name='DATA_FILE_INTERVAL' ;

　　set tableName=concat('dim_mailsendback_', year(now()),month(now()));

　　set @sql1=concat("select count(*) into @total from information_schema.tables where table_name ='",tableName,"' ");

　　set @sql2=concat('insert into postmail_back. ', tableName, ' select * from postmail.dim_mailsendback where (dayofyear(now())-dayofyear(sendtime)<=',intervalDay,')');

　　set @sql3=concat('create table postmail_back. ', tableName, ' select * from postmail.dim_mailsendback where (dayofyear(now())-dayofyear(sendtime)<=',intervalDay,')');

　　prepare stmt1 from @sql1;

　　execute stmt1;

　　deallocate prepare stmt1;

　　set total=@total;

　　if total=0 then

　　prepare stmt3 from @sql3;

　　execute stmt3;

　　deallocate prepare stmt3;

　　end if;

　　if total=1 then

　　prepare stmt2 from @sql2;

　　execute stmt2;

　　deallocate prepare stmt2;

　　end if;

　　END