Question

我有一个表student_course如下： -

student course
 1        a
 2        a
 1        b
 4        a
 5        d
 2        d
 5        a

我需要找到所有行，其中course = a，而课程不在b中。结果应该是： -

student course
 2        a
 4        a
 5        a

Answer 1

SELECT *
FROM student_course
WHERE course = 'a'
AND student NOT IN (SELECT student
                    FROM student_course
                    WHERE course = 'b');

Answer 2

SELECT * FROM student_course
WHERE course = 'a' AND student NOT IN 
(
 SELECT student FROM student_course a
 WHERE course = 'b' 
)

Answer 3

select student
from student_course 
group by student
having sum(case when course = 'a' then 1 else 0 end) > 0
and sum(case when course = 'b' then 1 else 0 end) = 0

Answer 4

尝试此查询：

SELECT ca.Student, ca.Course 
FROM student_course ca 
WHERE ca.course = 'a' 
    AND NOT EXISTS (SELECT 1 FROM student_course cb 
                    WHERE ca.Student = cb.Student AND cb.course = 'b' )

Answer 5

使用LEFT JOIN。

SELECT T1.*
FROM student_course T1
LEFT JOIN student_course T2 ON T1.student = T2.student AND T2.course = 'B'
WHERE T1.course = 'A' AND T2.student IS NULL

Answer 6

select * from student_course
where course = 'a' and student not in (select student from student_course where course = 'b')

使用SQL根据条件查找表中的记录

6 个答案: