HSQL语句，说说HSQL union all的用法

1、以前统计总量pv,uv和各分类的pv,uv都这么写也就是
SELECT a.type,a.pv,a.uv FROM 
(
   SELECT type,count(1) as pv,COUNT(distinct(uid))as uv 
   FROM t1 
   WHERE dt='201410129' AND req_url like 'mbloglist?domain=100808&ajwvr=6%' 
   group by type
 union all
   SELECT 'all' as type,count(1) as pv,COUNT(distinct(uid))as uv 
   FROM t1 
   WHERE dt='201410129' AND req_url like 'mbloglist?domain=100808&ajwvr=6%' 
) a
说明：distinct虽然写起来挺方便的，但是效率真的太差，建议永远不要用distinct
2、然后我们的语句就可以改为：
SELECT a.type,sum(pv),count(uid) FROM 
(
   SELECT type,count(1) as pv,uid
   FROM t1 
   WHERE dt='201410129' AND req_url like 'mbloglist?domain=100808&ajwvr=6%' 
   group by uid,type
 union all
   SELECT 'all' as type,count(1) as pv,uid
   FROM t1 
   WHERE dt='201410129' AND req_url like 'mbloglist?domain=100808&ajwvr=6%' 
   group by uid
) a
group by type
这样虽然效率提高了些，而且我也一直这么用了，有段时间，但总感觉还是很不爽，总觉得没有发挥union all的功能
3、今天才发现，这group by 不能写在里面，真的严重影响效率，而且按照上面写job数量还多，果断需改：
SELECT type,SUM(pv),count(uid) FROM (
SELECT a.type,sum(pv),uid FROM 
(
   SELECT type,1 as pv,uid
   FROM t1 
   WHERE dt='201410129' AND req_url like 'mbloglist?domain=100808&ajwvr=6%' 
 union all
   SELECT 'all' as type,1 as pv,uid
   FROM t1 
   WHERE dt='201410129' AND req_url like 'mbloglist?domain=100808&ajwvr=6%' 
) a
group by uid,type) b group by type
经测试，效率果然杠杠的