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Tác giả Quentin Cappart
Hạn chót Không có hạn chót
Giới hạn nộp bài Không có giới hạn

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Compréhension des mots-clefs (sous-requêtes imbriquées)

Parmi les propositions suivantes, trouvez celle donnant une description correcte des mots-clefs (ou requêtes) suivants.

Câu hỏi 1: 
select name
from student
where dept_name in (
  select dept_name
  from department
  where budget > 1000000
);
Câu hỏi 2: 
select name
from instructor
where exists (
   select *
   from teaches
   where teaches.ID = instructor.ID
);
Câu hỏi 3: 
select name
from instructor
where salary > some (
    select salary
    from instructor
    where dept_name = 'Biology'
);

Notez que l'opérateur some n'est malheureusement pas supporté par SQLite.

Câu hỏi 4: 
select name
from instructor
where salary > all (
    select salary
    from instructor
    where dept_name = 'Biology'
);

Notez que l'opérateur all n'est malheureusement pas supporté par SQLite.

Câu hỏi 5: 
with rich_departments as (
     select dept_name
     from department
     where budget > 50000
)
select name
from student
where dept_name in (select dept_name from rich_departments);