拆分字符串并循环遍历MySql过程中的值

I got a situation where I have to pass a comma separated string to MySQL procedure and split that string and insert those values as rows in to a table.

我遇到了一种情况，我必须将逗号分隔的字符串传递给MySQL过程并拆分该字符串并将这些值作为行插入到表中。

As show below

如下图所示

For example if I passed 'jhon,swetha,sitha' string to mysql procedure then it have to split that string by comma and insert those values as 3 records into a table.

例如，如果我将'jhon，swetha，sitha'字符串传递给mysql过程，则必须用逗号分割该字符串，并将这些值作为3条记录插入表中。

  CREATE PROCEDURE new_routine (IN str varchar(30))   
   BEGIN
       DECLARE tmp varchar(10);
       DECLARE inc INT DEFAULT 0; 
       WHILE INSTR(str, ',') DO
         SET tmp = SUBSTRING(SUBSTRING_INDEX(str,',',inc),LENGTH(SUBSTRING_INDEX(str,',',inc-1))+1),',','');
         SET str = REPLACE(str, tmp, '');
         //insert tmp into a table.
       END WHILE;
    END

But this does not worked any solution please.

但这不能解决任何问题。

1 个解决方案

#1

You'll need to be a little more careful with your string manipulation. You can't use REPLACE() for this, because that will replace multiple occurrences, corrupting your data if one element in the comma-separated list is a substring of another element. The INSERT() string function is better for this, not to be confused with the INSERT statement used for inserting into a table.

你需要对字符串操作更加小心。您不能使用REPLACE（），因为这将替换多次出现，如果逗号分隔列表中的一个元素是另一个元素的子字符串，则会破坏您的数据。 INSERT（）字符串函数对此更好，不要与用于插入表的INSERT语句混淆。

DELIMITER $$

DROP PROCEDURE IF EXISTS `insert_csv` $$
CREATE PROCEDURE `insert_csv`(_list MEDIUMTEXT)
BEGIN

DECLARE _next TEXT DEFAULT NULL;
DECLARE _nextlen INT DEFAULT NULL;
DECLARE _value TEXT DEFAULT NULL;

iterator:
LOOP
  -- exit the loop if the list seems empty or was null;
  -- this extra caution is necessary to avoid an endless loop in the proc.
  IF LENGTH(TRIM(_list)) = 0 OR _list IS NULL THEN
    LEAVE iterator;
  END IF;

  -- capture the next value from the list
  SET _next = SUBSTRING_INDEX(_list,',',1);

  -- save the length of the captured value; we will need to remove this
  -- many characters + 1 from the beginning of the string 
  -- before the next iteration
  SET _nextlen = LENGTH(_next);

  -- trim the value of leading and trailing spaces, in case of sloppy CSV strings
  SET _value = TRIM(_next);

  -- insert the extracted value into the target table
  INSERT INTO t1 (c1) VALUES (_next);

  -- rewrite the original string using the `INSERT()` string function,
  -- args are original string, start position, how many characters to remove, 
  -- and what to "insert" in their place (in this case, we "insert"
  -- an empty string, which removes _nextlen + 1 characters)
  SET _list = INSERT(_list,1,_nextlen + 1,'');
END LOOP;

END $$

DELIMITER ;

Next, a table for testing:

接下来，测试表：

CREATE TABLE `t1` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `c1` varchar(64) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

The new table is empty.

新表是空的。

mysql> SELECT * FROM t1;
Empty set (0.00 sec)

Call the procedure.

打电话给程序。

mysql> CALL insert_csv('foo,bar,buzz,fizz');
Query OK, 1 row affected (0.00 sec)

Note the "1 row affected" does not mean what you would expect. It refers to the last insert we did. Since we insert one row at a time, if the procedure inserts at least one row, you'll always get a row count of 1; if the procedure inserts nothing, you'll get 0 rows affected.

请注意，“受影响的1行”并不代表您的期望。它指的是我们做的最后一次插入。由于我们一次插入一行，如果过程插入至少一行，则总计得到行数为1;如果程序什么都不插入，你将受到0行的影响。

Did it work?

它有用吗？

mysql> SELECT * FROM t1;
+----+------+
| id | c1   |
+----+------+
|  1 | foo  |
|  2 | bar  |
|  3 | buzz |
|  4 | fizz |
+----+------+
4 rows in set (0.00 sec)