Implementation of mysql split function (separated by comma)

1: Define a stored procedure for delimiting strings

DELIMITER $$
USE `mess`$$
DROP PROCEDURE IF EXISTS `splitString`$$
CREATE DEFINER=`root`@`%` PROCEDURE `splitString`(IN f_string VARCHAR(1000),IN f_delimiter VARCHAR(5))
BEGIN    
    DECLARE cnt INT DEFAULT 0;    
    DECLARE i INT DEFAULT 0;    
    SET cnt = func_get_splitStringTotal(f_string,f_delimiter);    
    DROP TABLE IF EXISTS `tmp_split`;    
    CREATE TEMPORARY TABLE `tmp_split` (`val_` VARCHAR(128) NOT NULL) DEFAULT CHARSET=utf8;    
    WHILE i < cnt    
    DO    
        SET i = i + 1;    
        INSERT INTO tmp_split(`val_`) VALUES (func_splitString(f_string,f_delimiter,i));    
    END WHILE;    
END$$
DELIMITER ;

2: Implement the func_get_splitStringTotal function: this function is used to calculate the length after separation. Here are the functions to know:

REPLACE(str,from_str,to_str)

Returns the string str with all occurrences of the string from_str replaced by the string to_str. REPLACE() performs a case-sensitive match when searching for from_str.
E.g:
mysql> SELECT REPLACE('www.mysql.com', 'w', 'Ww');
        -> 'WwWwWw.mysql.com'

Implementation:

DELIMITER $$

USE `mess`$$

DROP FUNCTION IF EXISTS `func_get_splitStringTotal`$$

CREATE DEFINER=`root`@`%` FUNCTION `func_get_splitStringTotal`(    
f_string VARCHAR(10000),f_delimiter VARCHAR(50)    
) RETURNS INT(11)
BEGIN    
  RETURN 1+(LENGTH(f_string) - LENGTH(REPLACE(f_string,f_delimiter,'')));    
END$$

DELIMITER ;

3: Implement the func_splitString function: used to obtain the value of each loop after separation, here are the functions you need to know:

（1）REVERSE(str)

Returns the string str with the order of the characters reversed.
For example: mysql> SELECT REVERSE('abc');
        -> 'cba'

（2）
SUBSTRING_INDEX(str,delim,count)


Returns the substring from string str before count occurrences of the delimiter delim. If count is positive, everything to the left of the final delimiter (counting from the left) is returned. If count is negative, everything to the right of the final delimiter (counting from the right) is returned. SUBSTRING_INDEX() performs a case-sensitive match when searching for delim.

E.g:
mysql> SELECT SUBSTRING_INDEX('www.mysql.com', '.', 2);
        -> 'www.mysql'
mysql> SELECT SUBSTRING_INDEX('www.mysql.com', '.', -2);
        -> 'mysql.com'

Implementation:

DELIMITER $$

USE `mess`$$

DROP FUNCTION IF EXISTS `func_splitString`$$

CREATE DEFINER=`root`@`%` FUNCTION `func_splitString`( f_string VARCHAR(1000),f_delimiter VARCHAR(5),f_order INT) RETURNS VARCHAR(255) CHARSET utf8
BEGIN    
    DECLARE result VARCHAR(255) DEFAULT '';    
    SET result = REVERSE(SUBSTRING_INDEX(REVERSE(SUBSTRING_INDEX(f_string,f_delimiter,f_order)),f_delimiter,1));    
    RETURN result;    
END$$

DELIMITER ;

use:

(1) Call the stored procedure:

CALL splitString('1,3,5,7,9',',');

(2): View the temporary table

SELECT val_ FROM tmp_split AS t1;

result:

Implementation of mysql split function (separated by comma)

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