MYSQL 分组排名
今天遇到一个 MYSQL 排序的问题,要求按某列进行分组,组内进行排序.
百度一下发现 MYSQL 不支持 row_number(),rank()等函数.
采用的办法如下,我们首先创建一个测试表:
--创建表
create table Rank_test(ID int,SCORE int,grp int)
--插入数据
insert into Rank_test values(1 , 28,1);
insert into Rank_test values(2 , 33,1);
insert into Rank_test values(3 , 33,1);
insert into Rank_test values(4 , 89,1);
insert into Rank_test values(5 , 99,1);
insert into Rank_test values(6 , 68,1);
insert into Rank_test values(7 , 68,1);
insert into Rank_test values(8 , 78,1);
insert into Rank_test values(9 , 88,1);
insert into Rank_test values(10, 90 ,1);
insert into Rank_test values(11, 28,2);
insert into Rank_test values(12, 33,2);
insert into Rank_test values(13, 33,2);
insert into Rank_test values(14, 89,2);
insert into Rank_test values(15, 99,2);
insert into Rank_test values(16, 68,2);
insert into Rank_test values(17, 68,2);
insert into Rank_test values(18, 78,2);
insert into Rank_test values(19, 88,2);
insert into Rank_test values(20, 90 ,2);
分组排序的 SQL 代码:
SELECT id,
score,
rank
FROM (SELECT tmp.id,
tmp.score,
@rank := (case when @Grp = grp then @rank + 1 else 1 end) AS rank ,
@Grp:=grp as grp2
FROM (SELECT id,
score,
grp
FROM rank_test) tmp,
(SELECT @rank := 0,@grp:=0) a
order by grp,score desc) RESULT
;
结果如下:
测试结果 OK,但重点是套用到我们的 SQL 中后,排序结果完全不是我们预期中的,而且没有找到规律.
经过几次尝试,最后重新改写了 SQL 代码,终于成功了.
原因是套用下面这段代码时,我们是用了几张表进行关联(inner join ),最后将 inner join 的表全部改为 where 语句中的子句,结果满足我们的预期.?
(SELECT id,
score,
grp
FROM rank_test) tmp,
所以建议在这里的代码尽量使用单表,不要多张表关联
附上修改前后的代码:(修改前)
select * from (
select evtdate
,stkabb,chng,PCTCSHG,cshg,SHHNAME
,@rank := (case when @SHHNAME=SHHNAME then @rank + 1
else 1 end) AS rank
,@SHHNAME:=SHHNAME
from
(
select tt.SHHNAME -- 股东名称
,s.evtdate -- 变动日期
,r.stkabb -- 变动股票名称
,ifnull(s.RLDSHG,s.cshg-s.SHGBCH)/10000 as chng -- 变动股数（万股）
,s.cshg/10000 as cshg-- 变动后持股（万股）
,s.PCTCSHG -- 变动后持股比例 %
from pgenius.hk_stkcode r
inner join pgenius.HK_SAKCHMJSHH s
on r.comunic = s.comunic
inner join
(select distinct b.SHHNAME
from pgenius.hk_stkcode a
inner join pgenius.HK_SAKCHMJSHH b
on a.comunic = b.comunic
and b.evtdate = (select max(evtdate) from pgenius.HK_SAKCHMJSHH
where comunic = b.comunic and SHHNAME = b.SHHNAME and NTUREFCINTRTS = b.NTUREFCINTRTS)
where a.lssturefc = 1
and b.cshg > 0
and a.stkcode = '00001'
) tt
on s.SHHNAME = tt.SHHNAME
) t1,
(SELECT @rank := 0,@SHHNAME:='') t2
order by SHHNAME,evtdate desc,stkabb ) t
修改后
select t.*
, o.stkabb
from
(
select t1.*
,@rank
:= (case when @SHHNAME=SHHNAME then @rank + 1
else 1 end) AS rank
,@SHHNAME:=SHHNAME
from
(
select s.evtdate
,ifnull(s.RLDSHG,s.cshg-s.SHGBCH)/10000 as chng -- 变动股数（万股）
,s.cshg/10000 as cshg-- 变动后持股（万股）
,s.PCTCSHG -- 变动后持股比例 %
,SHHNAME
,s.COMUNIC
from pgenius.HK_SAKCHMJSHH s
where SHHNAME in (
select distinct shhname from pgenius.HK_SAKCHMJSHH a
where comunic=(select COMUNIC from pgenius.hk_stkcode where stkcode='00001')
and ISVALID=1
and not exists(select 1 from pgenius.HK_SAKCHMJSHH where COMUNIC=a.COMUNIC and SHHNAME=a.SHHNAME and evtdate>a.evtdate)
and cshg > 0)
) t1,
(SELECT @rank := 0,@SHHNAME:='') t2
order by SHHNAME,evtdate desc
) t
inner join pgenius.hk_stkcode o on t.COMUNIC= o.COMUNIC
where t.rank<=10
order by shhname,rank
最后附上本人修改的代码
SELECT
*, (
SELECT
rank
FROM
(
SELECT
s1id,
rname,
@rank := (
CASE
WHEN @Grp = rid THEN
@rank + 1
ELSE
1
END
) AS rank,
@Grp := rid AS grp2
FROM
(
SELECT
FROM
v_wx_mini_shop_user_info
) tmp,
(SELECT @rank := 0 ,@grp := 0) a
ORDER BY
rid DESC
) RESULT
WHERE
s1id = ssa.s1id
) AS crank,
(
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