mysql开发之---使用游标双层嵌套对总表进行拆分为帖子表和回复表，mysql游标
注意点：
（1）进行拆分的总表表名是不同的，所以创建临时表，把总表的数据先插入临时表
（2）为了避免最外层游标轮询数据结束时，抛出 not found 退出程序，不会执行关闭游标等后续操作，定义continue handler， declare continue handler for not found set done1=1;
1.1、外部存储过程调用主存储过程
CREATE PROCEDURE `bbs_split_thread_post_outer`(IN `in_tabname` varchar(128))
BEGIN
declare v_row_count int(11);
declare v_sql varchar(200);
-- 必须清空临时表bbs_fromask_importask_tmp
select sysdate();
truncate table bbs_fromask_importask_tmp;
set @sql=concat('insert into bbs_fromask_importask_tmp select * from ',in_tabname,';');
prepare stmt from @sql;
execute stmt;
call bbs_split_thread_post();
select sysdate();
END
CREATE PROCEDURE `bbs_split_thread_post`()
BEGIN
declare v_source_count int(11);
declare v_thread_pkid int(11);
declare v_thread_pkid_uni_count int(11);
declare done1,done2 int default 0;
declare v_cur_thread_pkid cursor for select pkid,count(*) from bbs_fromask_importask_tmp group by pkid;
declare continue handler for not found set done1=1;
-- 清空临时表
truncate table pre_data_thread_tmp;
truncate table pre_data_post_tmp;
-- 判断原表是否有数据，没有什么也不做
select count(*) into v_source_count from bbs_fromask_importask_tmp;
if v_source_count>0 then
select ifnull(max(id),0) into @thread_max_id from yaolanbbs.pre_data_thread; -- 可做修改
select @thread_max_id;
-- 打开游标
open v_cur_thread_pkid;
repeat
fetch v_cur_thread_pkid into v_thread_pkid,v_thread_pkid_uni_count;
-- 每次fetch最大id自增1
if not done1 then
set @thread_max_id=@thread_max_id+1;
insert into pre_data_thread_tmp(id,title,age,rule,param)
select @thread_max_id,t1.qtitle,t1.age,'age',t1.age from bbs_fromask_importask_tmp t1 where t1.pkid=v_thread_pkid limit 1;
-- 根据pkid对一组数据进行处理
begin
declare v_post_answer text;
declare v_cur_post_record cursor for select t1.answer from bbs_fromask_importask_tmp t1 where t1.pkid=v_thread_pkid;
declare exit handler for not found close v_cur_post_record;
-- declare continue handler for not found set done2=1;
insert into pre_data_post_tmp(tid,text,sort)
select @thread_max_id,t1.qdesc,1 from bbs_fromask_importask_tmp t1 where t1.pkid=v_thread_pkid limit 1;
set @sort=2; ######设置值
open v_cur_post_record;
repeat
fetch v_cur_post_record into v_post_answer;
-- select @sort;
-- select v_post_answer;
insert into pre_data_post_tmp(tid,text,sort) values(@thread_max_id,v_post_answer,@sort);
-- insert into testincre values(@sort,v_post_answer);
set @sort=@sort+1;
until 0 end repeat;
-- select curdate(); 不会执行的原因，定义exit handler
close v_cur_post_record;
end;
end if;
until done1 end repeat;
-- 关闭游标
close v_cur_thread_pkid;
-- select curdate();
/*-- 导入最终表
insert into pre_data_thread(id,title,create_time,age,rule,param)
select id,title,create_time,age,rule,param from pre_data_thread_tmp;
insert into pre_data_post(tid,text,sort,create_time)
select tid,text,sort,create_time from pre_data_post_tmp;
*/
end if;
END
总结：
（1）30G内存没有负载的情况下，8488276行拆为两个表共10500000行用时39分钟
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