php - 使用 mysql 将表列中的逗号分隔值拆分为行？

Question

我找到了 post其中包含由逗号分隔的 3 个值的列。我将有 3 个以上的值，用逗号分隔。例如，

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

是否可以像下面这样使用 mysql 查询拆分字符串 city_id 并将其放入行中

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

如果是，请给点建议....

Answer 1

试试这个

  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

FIDDLE DEMO

输出:

---

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