基于第一个多响应的第二个表上的SQL查询

Question

这是一个SQL查询,如果首先返回多个值,则会失败

SELECT     subject
FROM         a_batchcourse_subject AS s
WHERE     (batchcourse =
                          (SELECT     batchcourse
                          FROM          a_course_batchcourse AS b
                          WHERE      (course = 'Course 1')))

在第一个查询可能返回多个值的情况下编写此查询的正确方法是什么？

Answer 1

你想IN在sql中没有=

SELECT subject
FROM a_batchcourse_subject AS s
WHERE batchcourse IN
(SELECT batchcourse
FROM a_course_batchcourse AS b
WHERE course = 'Course 1')