[oracle/sql]写SQL从学生考试成绩三表中选出五门分综合超过720的尖子

任务：有学生，科目，考分三张表，需要从中筛选出五门考分总和超过720的学生。

科目表最简单只有五条记录：

CREATE TABLE tb_course
(
    id NUMBER not null primary key,
    name NVARCHAR2(10) not null
)

Insert into tb_course(id,name) values('','语文');
Insert into tb_course(id,name) values('','数学');
Insert into tb_course(id,name) values('','英语');
Insert into tb_course(id,name) values('','物理');
Insert into tb_course(id,name) values('','化学');

学生表只有两个字段，但数据量却有十万：

CREATE TABLE tb_student
(
    id NUMBER not null primary key,
    name NVARCHAR2(20) not null
)

Insert into tb_student
 select rownum,dbms_random.string('*',dbms_random.value(15,20)) from dual
 connect by level<=100000
 order by dbms_random.random

成绩表很庞大，需要在其中创建共两百万条数据：

CREATE TABLE tb_score
(
    id NUMBER not null primary key,
    studentid int not null,
    courseid int not null,
    score int not null
)

Insert into tb_score
select rownum,dbms_random.value(0,100000),dbms_random.value(1,5),dbms_random.value(0,150) from dual
connect by level<=2000000
order by dbms_random.random

执行完毕以后commit.

现在可否开始查询呢？还不行，我们需要把每个考生单科最高分数据遴选出来，放到一张新表中。

create table tb_score2 as
select * from tb_score where (studentid,courseid,score) in(
select studentid,courseid,max(score) as score from tb_score
group by studentid,courseid) 

在我实验中，新表中约有49万数据，是原表的四分之一。

那么为什么不删除tb_score表中不是每个考生单科最高分那些记录呢，比如用下来的sql去删：

delete from tb_score where id not in(
select id from tb_score where (studentid,courseid,score) not in(
select studentid,courseid,max(score) as score from tb_score
group by studentid,courseid) )

是因为这样删除实在是太慢了，我浏览了百度新闻，51job首页和电影港首页居然还没完，选出数据放到新表会快得多。

然后用以下语句就能找出五门总分在720以上的学生：

select stu.id,stu.name,sco.sumscore from tb_student stu,
(select new_score.studentid,new_score.sumscore,new_score.cids from
(select studentid,sum(score) as sumscore,(listagg(courseid,',') within group (order by courseid)) as cids from tb_score2
group by studentid ) new_score where new_score.cids=(select listagg(id,',') within group (order by id) from tb_course)
and new_score.sumscore>720 ) sco
where stu.id=sco.studentid
order by sco.sumscore desc

让我们看看这些英才都是哪些人：

SQL> select stu.id,stu.name,sco.sumscore from tb_student stu,
  2  (select new_score.studentid,new_score.sumscore,new_score.cids from
  3  (select studentid,sum(score) as sumscore,(listagg(courseid,',') within group (order by courseid)) as cids from tb_score2
  4  group by studentid ) new_score where new_score.cids=(select listagg(id,',') within group (order by id) from tb_course)
  5  and new_score.sumscore>720 ) sco
  6  where stu.id=sco.studentid
  7  order by sco.sumscore desc;

        ID NAME                                       SUMSCORE
---------- ---------------------------------------- ----------
     60230 MGHSGQWZZLWTMHAFCK                              738
     98913 FCIJHDBJDKUCLFTIOLR                             737
     19881 OWWHEDLATQLSUVXF                                736
      8711 UOAOGXWBATDMYBFM                                736
     26842 MUVPTHSTPNSKWSXIFAPP                            735
     58112 GOGZBZKYIZQBAYQS                                735
     42644 ZCWWQFSGOZMDFMS                                 735
     42177 XDRUJHTZTOJVSFGI                                734
     56021 FBYUWGMGZORIQBXLTHO                             733
     65292 HUOUBIIWJNLAOGZW                                733
     87009 EBMPZNHSZMXMTSUC                                732

        ID NAME                                       SUMSCORE
---------- ---------------------------------------- ----------
     83641 VKEKWTDNFDHXZRRPWIYD                            731
     58593 ZECIYJCZNYMUSNTG                                731
     32116 PZXWQZXAYLVAWNYG                                729
     97616 FGQGNKHTPDHHWOUU                                729
     74935 QNEHWSJTFLOSMXB                                 729
     66747 WJURFLHNXQFDKNNOVT                              729
     49933 WGGGACVVJXXCODNLLB                              729
     23554 JKUNYBSSEKXQCVWE                                728
     55634 TCLLHZESREMRLIIWRUK                             727
      9387 EMYCJDHYLAXSGKE                                 726
     93450 KQSBMYGSCRETYKYSYK                              726

        ID NAME                                       SUMSCORE
---------- ---------------------------------------- ----------
     76314 NHOPFXSAYNKHSKHZJNY                             726
     76186 TXVXNSZETKCGLLX                                 726
     61658 KSVTBNNAAJWZVVHP                                726
     33200 KJZXFGIDCJRRNKWNKG                              726
     84699 TDWMXMJRJTFCLGTC                                726
     86265 HBMIDMWVXMESKIIIQFPV                            726
     63956 MGPVABXLFQVKMKOQHN                              725
     33717 ABVGWFOAMIEQGIXIHBS                             725
     96610 OYOIJZGDXHWHTFNUDL                              725
     13104 KXCWLAUGOZSKQWTL                                724
     91912 MJYPLBSMWPEOLXUGGD                              724

        ID NAME                                       SUMSCORE
---------- ---------------------------------------- ----------
     83508 IBNWASUMLVNLBXCURX                              724
     50997 YETMKRMKNAYMQQORGB                              724
     33868 WBXWDFIALHEAPPHKRAM                             724
     20391 RDHGEGGOIGVWTNJMJ                               724
     70595 SMVMJFVMDIYUNWYXC                               724
      8865 EYZZZGOAJNUENIXT                                723
     73241 DYMNRSECWZYLWFI                                 723
     60378 YYQYSKIVBITGICD                                 723
     13578 TLGLDLAYPRRCFTWQKRX                             723
     27338 HPAMAIQHHQNKDYJ                                 723
     41174 HPMAFEVRCXEBVRRVEBYI                            723

        ID NAME                                       SUMSCORE
---------- ---------------------------------------- ----------
     93860 VVXTQWGQGPEALAN                                 723
     89181 AUAVRUBGTVEQISOBAFP                             723
     87519 MFOWKQSBTJVRJXX                                 723
     83007 OZOYETVCZMJNXSIOSX                              723
     85947 DXSJSSMEMCJAIIGT                                722
     52919 FXELVCEHUAUMPHRKONX                             722
     94309 NTOCAERVSKNGLEZNIZ                              722
     34681 ZYOXMRWYYOVWONLNDR                              722
     30518 JNPYQNNWBPSKICREMPE                             722
     49635 MTJFGEKFQREYUQWPEWF                             722
     80760 LLHVLFAKXVSHTVYHOC                              722

        ID NAME                                       SUMSCORE
---------- ---------------------------------------- ----------
     57707 SLYATRQZDXZYFVEM                                722
     18030 QZMPAWQKYISWWTSWM                               722
     74491 JLKIFEQCCLFCFIEFW                               722
     43296 VBLZPERIAXJYYYSTI                               722
     80816 IQSGRNLVHELBTSLGZ                               722
     92947 JHXVIRBODOUDZMMWP                               722
      5212 LCSFRFCWAFTLFPBWLU                              721
      9299 RUTLPLEFYYDVKLHPLK                              721
     10058 VBPVPMMAXRZIZLXHEI                              721
     10361 GBIXPYTHTZZWDPKW                                721
     15331 UMJLKKQHAKKBAOH                                 721

        ID NAME                                       SUMSCORE
---------- ---------------------------------------- ----------
     28393 LDLWTKPQSXLRWYN                                 721
     39285 RIIBDINLLFXHETSPA                               721
     46517 TNUZAIUCZKWBFAGWEV                              721
     58569 ZINHWFNOOTQPEQOA                                721
     60567 UDECJDCGZIZZWUM                                 721
     61563 SXBXGEBVXVNKSCWTUHLW                            721
     66670 XZYWNVSUWZWRYVYTVD                              721
     68668 FSAKVTSSBMYFPOSPSLG                             721
     91083 MGZJEJCGBSXEANPBHZK                             721
     92262 QKMPVBTYMXUVOGSAL                               721
     95418 QZQFIHRMNIGCDXSYHE                              721

        ID NAME                                       SUMSCORE
---------- ---------------------------------------- ----------
     99418 HMKXSDFBGRETSZXYX                               721

已选择78行。

2020年1月23日