使用mysql将表列中的逗号分隔值拆分为行？

Question

我找到了一个帖子，其中列有 3 个用逗号分隔的值。我将有超过 3 个以逗号分隔的值。例如，

ID    CITY_ID
--------------
1     12,18,16,17,35
2     12,16
....
--------------

是否可以使用如下所示的 mysql 查询将字符串 city_id 拆分为行

  ID   CITY_ID
  -------------
   1    12
   1    18
   1    16
    ....
   2    16
    ....
  --------------

如果是的话，请给一些建议......

Answer 1

尝试这个

  SELECT ID,SUBSTRING_INDEX(SUBSTRING_INDEX(t.CITY_ID, ',', n.n), ',', -1) value
  FROM Table1 t CROSS JOIN 
  (
   SELECT a.N + b.N * 10 + 1 n
     FROM 
    (SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) a
   ,(SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) b
    ORDER BY n 
   ) n
 WHERE n.n <= 1 + (LENGTH(t.CITY_ID) - LENGTH(REPLACE(t.CITY_ID, ',', '')))
 ORDER BY ID,value

小提琴演示

输出：

ID  VALUE
1   12
1   16
1   17
1   18
1   35
2   12
2   16