拆分字符串并循环遍历MySql过程中的值 [英] Split a string and loop through values in MySql Procedure
问题描述
我遇到了这样一种情况,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,然后将这些值作为行插入表中.
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.
如下所示
例如,如果我将'jhon,swetha,sitha'字符串传递给mysql过程,则它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.
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.
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
但这不能解决任何问题.
But this does not worked any solution please.
推荐答案
您需要在字符串操作上多加注意.您不能为此使用REPLACE()
,因为如果逗号分隔列表中的一个元素是另一元素的子字符串,则它将替换多次出现的数据,从而破坏数据. INSERT()
字符串函数更适合这,不要与用于插入表中的INSERT
语句相混淆.
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.
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 (_value);
-- 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 ;
接下来,要进行测试的表格:
Next, a table for testing:
CREATE TABLE `t1` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`c1` varchar(64) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
新表为空.
mysql> SELECT * FROM t1;
Empty set (0.00 sec)
调用该过程.
mysql> CALL insert_csv('foo,bar,buzz,fizz');
Query OK, 1 row affected (0.00 sec)
请注意,受影响的第一行"并不表示您期望的结果.它指的是我们所做的最后一次插入.由于我们一次插入一行,因此,如果该过程至少插入 一行,则您将始终获得1的行数;否则,如果该过程未插入任何内容,则将影响0行.
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.
它起作用了吗?
mysql> SELECT * FROM t1;
+----+------+
| id | c1 |
+----+------+
| 1 | foo |
| 2 | bar |
| 3 | buzz |
| 4 | fizz |
+----+------+
4 rows in set (0.00 sec)
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