Question

我的代码：

drop table if exists HSstudents;

create table HSstudents 
(
     HSsID int, 
     vNAAM text, 
     aNAAM text, 
     LT int, 
     GM float
);

insert into HSstudents values (1, 'Thomas', 'Jansen', 18, 7.0);
insert into HSstudents values (2, 'Jesse', 'Bakker', 19, 6.5);
insert into HSstudents values (3, 'Tom', 'Smit', 20, 7.1);
insert into HSstudents values (4, 'Jelle', 'Visser', 17, 9.6);
insert into HSstudents values (5, 'Sem', 'Dekker', 17, 8.1);
insert into HSstudents values (6, 'Anna', 'Peters', 18, 6.8);
insert into HSstudents values (7, 'Michelle', 'Hendriks', 19, 8.2);
insert into HSstudents values (8, 'Senna', 'Mulder', 20, 5.9);
insert into HSstudents values (9, 'Sven', 'Linden', 21, 6.0);
insert into HSstudents values (10, 'Ilse', 'Jacobs', 21, 7.5);
insert into HSstudents values (11, 'Harm', 'Schouten', 19, 7.0);
insert into HSstudents values (12, 'Emma', 'Dijkstra', 18, 8.1);

drop table if exists students;

create table students 
(
     sID int, 
     vNAAM text, 
     aNAAM text, 
     LT int
);

insert into students values (1, 'Thomas', 'Jansen', 18);
insert into students values (2, 'Jesse', 'Bakker', 19);
insert into students values (3, 'Tom', 'Smit', 20);
insert into students values (4, 'Jelle', 'Visser', 17);
insert into students values (5, 'Sem', 'Dekker', 17);
insert into students values (6, 'Anna', 'Peters', 18);
insert into students values (7, 'Michelle', 'Hendriks', 19);
insert into students values (8, 'Senna', 'Mulder', 20);
insert into students values (9, 'Sven', 'Linden', 21);
insert into students values (10, 'Ilse', 'Jacobs', 21);
insert into students values (11, 'Harm', 'Schouten', 19);
insert into students values (12, 'Emma', 'Dijkstra', 18);

drop table if exists applications;

create table applications 
(
    sID int, 
    aPROV text, 
    sPROV text, 
    taal text
);

insert into applications values (1, 'Overijssel', 'Drenthe', 'HTML');
insert into applications values (2, 'Gelderland', 'Overijssel', 'CSS');
insert into applications values (3, 'Groningen', 'Flevoland', 'CSS');
insert into applications values (4, 'Overijssel', 'Zuid-Holland', 'SQL');
insert into applications values (5, 'Noord-Holland', 'Drenthe', 'C#');
insert into applications values (6, 'Flevoland', 'Groningen', 'C#');
insert into applications values (7, 'Limburg', 'Groningen', 'JAVA');
insert into applications values (8, 'Limburg', 'Limburg', 'JAVASCRIPT');
insert into applications values (9, 'Drenthe', 'Noord-Brabant', 'CSS');
insert into applications values (10, 'Drenthe', 'Zeeland', 'Python');
insert into applications values (11, 'Zuid-Holland', 'Friesland', 'C++');
insert into applications values (12, 'Zeeland', 'Friesland', 'JAVA');

select 
    S.sID, S.vNAAM, S.aNAAM, S.LT, aPROV, sPROV, taal
from 
    HSstudents HS, students S, applications A
where 
    HSstudents.HSsID = students.sID

这会导致错误

代码：1054。未知专栏＆＃39; HSstudents.HSsID＆＃39;在＆＃39; where子句＆＃39;

如何？难道它不能正常工作吗？

Answer 1

WHERE子句应遵循FROM子句的剩余：

where HS.HSsID = S.sID

where子句中的未知列？

1 个答案: