Split value from one field to two

Question

I\'ve got a table field membername which contains both the last name and the first name of users. Is it possible to split those into 2 fields memberfirst<

Answer 1

In case someone needs to run over a table and split a field:

1. First we use the function mention above:

CREATE DEFINER=`root`@`localhost` FUNCTION `fn_split_str`($str VARCHAR(800), $delimiter VARCHAR(12), $position INT) RETURNS varchar(800) CHARSET utf8
    DETERMINISTIC
BEGIN 
    RETURN REPLACE(
            SUBSTRING(
                SUBSTRING_INDEX($str, $delimiter, $position),
                LENGTH(
                    SUBSTRING_INDEX($str, $delimiter, $position -1)
                ) + 1
            ),
    $delimiter, '');
END

2. Second, we run in a while loop on the string until there isn't any results (I've added $id for JOIN clause):

CREATE DEFINER=`root`@`localhost` FUNCTION `fn_split_str_to_rows`($id INT, $str VARCHAR(800), $delimiter VARCHAR(12), $empty_table BIT) RETURNS int(11)
BEGIN

    DECLARE position INT;
    DECLARE val VARCHAR(800);
    SET position = 1;
    
    IF $empty_table THEN
        DROP TEMPORARY TABLE IF EXISTS tmp_rows;    
    END IF;
            
    SET val = fn_split_str($str, ',', position);
            
    CREATE TEMPORARY TABLE IF NOT EXISTS tmp_rows AS (SELECT $id as id, val as val where 1 = 2);
        
    WHILE (val IS NOT NULL and val != '') DO               
        INSERT INTO tmp_rows
        SELECT $id, val;
        
        SET position = position + 1;
        SET val = fn_split_str($str, ',', position);
    END WHILE;
    
    RETURN position - 1;
END

3. Finally we can use it like that:

DROP TEMPORARY TABLE IF EXISTS tmp_rows;
SELECT  SUM(fn_split_str_to_rows(ID, FieldToSplit, ',', 0))
FROM    MyTable;

SELECT * FROM tmp_rows;

You can use the id to join to other table.

In case you are only splitting one value you can use it like that

SELECT  fn_split_str_to_rows(null, 'AAA,BBB,CCC,DDD,EEE,FFF,GGG', ',', 1);
SELECT * FROM tmp_rows;

We don't need to empty the temporary table, the function will take care of that.