MySql：存儲過程的拆分，返回表

Question

我發現了很多MySql的拆分過程示例，這些示例返回字符串的xth部分。 但是我需要一個拆分過程來返回拆分字符串的所有部分，所以像這樣：

SELECT split(",", "1,2,3,4,5,6");

應該返回；

+-------+
| split |
+-------+
|     1 |
|     2 |
|     3 |
|     4 |
|     5 |
|     6 |
+-------+

我試過了：

DELIMITER $$

CREATE PROCEDURE `split`(delimeter VARCHAR(1),txt VARCHAR(65535))
RETURNS split TABLE (
  part varchar(1024) NOT NULL)
DETERMINISTIC
BEGIN

DECLARE pos, posOld;

set pos := locate(delimeter,txt);
set posOld = 1;

WHILE pos > 0 DO
 set part := subst(text, posOld, pos-1);
 set posOld := pos+1;
 insert into split (`part`) values (part);

 set pos := locate(delimeter, txt, posOld);
END WHILE;

END$$

但得到錯誤：

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'split TABLE (part varchar(1024) NOT NULL)

正確的方法是什么？

Answer 1

您只能使用純SQL執行此操作。
此技巧是通過將MySQL數字生成器與嵌套的SUBSTRING_INDEX函數結合使用。

詢問

此查詢將生成1到100之間的數字。
因此，最終查詢最多可支持100個分隔的值。

SELECT 
 (@number  := @number + 1) AS number
FROM (
  SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
) AS record_1
CROSS JOIN (
  SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
) AS record_2
CROSS JOIN ( SELECT @number := 0 ) AS init_user_param

參見演示http://sqlfiddle.com/#!9/c314ca/5

現在，我們將使用逗號分隔的字符串提取值

詢問

將[position]替換為0到5之間的數字，您要從逗號分隔的字符串中提取該值。

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX('1,2,3,4,5', ',', [position]), ',', -1) AS split;

參見演示http://sqlfiddle.com/#!9/c314ca/16

現在我們知道了將兩個查詢結合到一個可行的解決方案中的基礎知識。

詢問

SELECT
  DISTINCT 
    SUBSTRING_INDEX(SUBSTRING_INDEX(@CSV, ',', generator.number), ',', -1) AS split
FROM (

  SELECT 
   (@number  := @number + 1) AS number
  FROM (
    SELECT 0 UNION SELECT 1 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
  ) AS record_1
  CROSS JOIN (
    SELECT 0 UNION SELECT 1 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
  ) AS record_2
  CROSS JOIN ( SELECT @number := 0 ) AS init_user_param
) 
 AS generator
CROSS JOIN (
  SELECT @CSV := '1,2,3,4,5'
) AS init_user_param

參見演示http://sqlfiddle.com/#!9/c314ca/20