如何使用第一个表中的逗号分隔值从另一个表中选择行？ [复制]

Question

有没有办法使用第一个表中的逗号分隔值从另一个表中选择行？

表 1.faculty

subject
101, 102
104
103, 105

表 2.subject

code	subject
101	subject 1
102	subject 2
103	subject 3
104	subject 4
105	subject 5

预期输出：

subject	subject
101, 102	subject 1, subject 2
104	subject 4
103, 105	subject 3, subject 5

我已经试过了：

SELECT faculty.subject, subject_offered.code, subject_offered.subject 
       FROM faculty 
       LEFT JOIN subject_offered 
       ON subject_offered.code 
       IN (faculty.subject)

但faculty 中具有多个值（逗号分隔）的行在subject 表的代码和主题列中显示为NULL。

my output

Answer 1

    SELECT  f.subject,
            GROUP_CONCAT(s.subject  ) as subject
    FROM    faculty as f
    INNER JOIN subjects s
        ON FIND_IN_SET(s.code, f.subject) 
    GROUP BY f.subject;

Run in Fiddle

Answer 2

更新

请参阅the answer by @Akina 以获得完整正确和更清洁的解决方案。

虽然这是一个非常糟糕的表格设计，但仍有办法解决这个问题。

解决方案

SELECT faculty_subject AS faculty_subject_codes, GROUP_CONCAT(subject ORDER BY code ASC) AS subjects
FROM (
  SELECT faculty.subject as faculty_subject, subject.*
FROM subject
JOIN faculty 
ON faculty.subject LIKE CONCAT('%', subject.code, '%')
) fa GROUP BY faculty_subject;

给予

faculty_subject_codes	subjects
101,102	subject 1,subject 2
103,105	subject 3,subject 5
104	subject 4

结帐my fiddle for your question

说明

由于faculty.subject 是逗号分隔值，因此您不能通过subject.code 进行常规连接，解决方法是使用JOIN 和LIKE 子句代替。

SELECT faculty.subject as faculty_subject, subject.*
FROM subject
JOIN faculty 
ON faculty.subject LIKE CONCAT('%', subject.code, '%');

faculty_subject	code	subject
101,102	101	subject 1
101,102	102	subject 2
103,105	103	subject 3
104	104	subject 4
103,105	105	subject 5

现在我们有多个具有相同的 Faculty_subject 的行，例如代码 103 和 105。接下来是将这些重复的行合并到一个条目中，我们将使用 GROUP CONCAT 语句和 GROUP BY 来执行此操作faculty_subject

SELECT faculty_subject AS faculty_subject_codes, GROUP_CONCAT(subject ORDER BY code ASC) AS subjects
FROM (
  SELECT faculty.subject as faculty_subject, subject.*
FROM subject
JOIN faculty 
ON faculty.subject LIKE CONCAT('%', subject.code, '%')
) fa GROUP BY faculty_subject;

Answer 3

SELECT t1.subject, GROUP_CONCAT(t2.subject)
FROM faculty t1
JOIN subjects t2 ON FIND_IN_SET(t2.code, t1.subject)
GROUP BY t1.subject;

https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=3e40ab353ff1e0a1cde678225fa63ed2