需求：
查询规则自定义，由数据库保存，返回结果字段来自同一张表；
要实现多个规则查询条件符合的适配，最终将查询结果合并展示出来，并标注是哪个规则的结果；
Mysql例子
--合并重复行 select * from A union select * from B --不合并重复行 select * from A union all select * from B Select * From (select id,adddate,title,url from bArticle where ClassId=1 order by adddate desc limit 0,2) A Union All Select * From (select id,adddate,title,url from bArticle where ClassId=2 order by adddate desc limit 0,2) B Union All Select * From (select id,adddate,title,url from bArticle where ClassId=3 order by adddate desc limit 0,2) C Union AllSelect * From (select id,adddate,title,url from bArticle where ClassId=4 order by adddate desc limit 0,2) D
实践：
这里使用的是mysql默认的数据库mysql
SELECT * FROM (SELECT *,(SELECT 'A' as A) tag FROM help_topic) A UNION ALLSELECT * FROM (SELECT *,(SELECT 'B' as A) tag FROM help_topic) B UNION ALLSELECT * FROM (SELECT *,(SELECT 'C' as A) tag FROM help_topic) C UNION ALLSELECT * FROM (SELECT *,(SELECT 'D' as A) tag FROM help_topic) D
效果图：
