37

我似乎经常遇到这个问题，我的数据格式如下：

+----+----------------------+
| id | colors               |
+----+----------------------+
| 1  | Red,Green,Blue       |
| 2  | Orangered,Periwinkle |
+----+----------------------+

但我希望它的格式如下：

+----+------------+
| id | colors     |
+----+------------+
| 1  | Red        |
| 1  | Green      |
| 1  | Blue       |
| 2  | Orangered  |
| 2  | Periwinkle |
+----+------------+

有没有好的方法来做到这一点？这种操作到底叫什么？

4

6 回答 6

24

您可以使用这样的查询：

SELECT
  id,
  SUBSTRING_INDEX(SUBSTRING_INDEX(colors, ',', n.digit+1), ',', -1) color
FROM
  colors
  INNER JOIN
  (SELECT 0 digit UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3) n
  ON LENGTH(REPLACE(colors, ',' , '')) <= LENGTH(colors)-n.digit
ORDER BY
  id,
  n.digit

请在此处查看小提琴。请注意，此查询每行最多支持 4 种颜色，您应该更新您的子查询以返回超过 4 个数字（或者您应该使用包含 10 或 100 个数字的表）。

于 2013-06-25T22:36:20.507 回答
14

我认为这是你需要的（存储过程）：Mysql split column string into rows

DELIMITER $$

DROP PROCEDURE IF EXISTS explode_table $$
CREATE PROCEDURE explode_table(bound VARCHAR(255))

BEGIN

DECLARE id INT DEFAULT 0;
DECLARE value TEXT;
DECLARE occurance INT DEFAULT 0;
DECLARE i INT DEFAULT 0;
DECLARE splitted_value INT;
DECLARE done INT DEFAULT 0;
DECLARE cur1 CURSOR FOR SELECT table1.id, table1.value
                                     FROM table1
                                     WHERE table1.value != '';
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

DROP TEMPORARY TABLE IF EXISTS table2;
CREATE TEMPORARY TABLE table2(
`id` INT NOT NULL,
`value` VARCHAR(255) NOT NULL
) ENGINE=Memory;

OPEN cur1;
  read_loop: LOOP
    FETCH cur1 INTO id, value;
    IF done THEN
      LEAVE read_loop;
    END IF;

    SET occurance = (SELECT LENGTH(value)
                             - LENGTH(REPLACE(value, bound, ''))
                             +1);
    SET i=1;
    WHILE i <= occurance DO
      SET splitted_value =
      (SELECT REPLACE(SUBSTRING(SUBSTRING_INDEX(value, bound, i),
      LENGTH(SUBSTRING_INDEX(value, bound, i - 1)) + 1), ',', ''));

      INSERT INTO table2 VALUES (id, splitted_value);
      SET i = i + 1;

    END WHILE;
  END LOOP;

  SELECT * FROM table2;
 CLOSE cur1;
 END; $$
于 2013-06-25T22:45:15.503 回答
2

这为我节省了很多时间！更进一步：在一个典型的实现中，很可能会有一个表，它根据标识键枚举颜色，color_list. 无需修改查询即可将新颜色添加到实现中，并且union可以通过将查询更改为以下内容来完全避免潜在的无穷无尽的子句：

SELECT id,
  SUBSTRING_INDEX(SUBSTRING_INDEX(colors, ',', n.digit+1), ',', -1) color
FROM
  colors
  INNER JOIN
  (select id as digit from color_list) n
  ON LENGTH(REPLACE(colors, ',' , '')) <= LENGTH(colors)-n.digit
ORDER BY id, n.digit;

然而，表 color_list 中的 ID 保持顺序很重要。

于 2015-06-19T14:19:55.420 回答
1

不需要存储过程。一个 CTE 就足够了：

CREATE TABLE colors(id INT,colors TEXT);
INSERT INTO colors VALUES (1, 'Red,Green,Blue'), (2, 'Orangered,Periwinkle');

WITH RECURSIVE
  unwound AS (
    SELECT *
      FROM colors
    UNION ALL
    SELECT id, regexp_replace(colors, '^[^,]*,', '') colors
      FROM unwound
      WHERE colors LIKE '%,%'
  )
  SELECT id, regexp_replace(colors, ',.*', '') colors
    FROM unwound
    ORDER BY id
;

+------+------------+
| id   | colors     |
+------+------------+
|    1 | Red        |
|    1 | Green      |
|    1 | Blue       |
|    2 | Orangered  |
|    2 | Periwinkle |
+------+------------+
于 2021-05-27T17:13:33.233 回答
0

如果定界符是数据的一部分但被双引号嵌入，那么我们如何拆分它。

示例第一，“第二，s”，第三

它应该是第一秒，第三秒

于 2018-10-10T02:53:20.870 回答
0

请注意，这可以在不创建临时表的情况下完成

select id, substring_index(substring_index(genre, ',', n), ',', -1) as genre
from my_table
join 
(SELECT @row := @row + 1 as n FROM 
(select 0 union all select 1 union all select 3 union all select 4 union all select 5 union all select 6 union all select 6 union all select 7 union all select 8 union all select 9) t,
(SELECT @row:=0) r) as numbers
  on char_length(genre) 
    - char_length(replace(genre, ',', ''))  >= n - 1
于 2016-03-01T17:08:25.313 回答