Split value from one field to two

Unfortunately MySQL does not feature a split string function. However you can create a user defined function for this, such as the one described in the following article:

• MySQL Split String Function by Federico Cargnelutti

With that function:

DELIMITER $$

CREATE FUNCTION SPLIT_STR(
  x VARCHAR(255),
  delim VARCHAR(12),
  pos INT
)
RETURNS VARCHAR(255) DETERMINISTIC
BEGIN 
    RETURN REPLACE(SUBSTRING(SUBSTRING_INDEX(x, delim, pos),
       LENGTH(SUBSTRING_INDEX(x, delim, pos -1)) + 1),
       delim, '');
END$$

DELIMITER ;

you would be able to build your query as follows:

SELECT SPLIT_STR(membername, ' ', 1) as memberfirst,
       SPLIT_STR(membername, ' ', 2) as memberlast
FROM   users;

If you prefer not to use a user defined function and you do not mind the query to be a bit more verbose, you can also do the following:

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(membername, ' ', 1), ' ', -1) as memberfirst,
       SUBSTRING_INDEX(SUBSTRING_INDEX(membername, ' ', 2), ' ', -1) as memberlast
FROM   users;

SELECT variant (not creating a user defined function):

SELECT IF(
        LOCATE(' ', `membername`) > 0,
        SUBSTRING(`membername`, 1, LOCATE(' ', `membername`) - 1),
        `membername`
    ) AS memberfirst,
    IF(
        LOCATE(' ', `membername`) > 0,
        SUBSTRING(`membername`, LOCATE(' ', `membername`) + 1),
        NULL
    ) AS memberlast
FROM `user`;

This approach also takes care of:

• membername values without a space: it will add the whole string to memberfirst and sets memberlast to NULL.
• membername values that have multiple spaces: it will add everything before the first space to memberfirst and the remainder (including additional spaces) to memberlast.

The UPDATE version would be:

UPDATE `user` SET
    `memberfirst` = IF(
        LOCATE(' ', `membername`) > 0,
        SUBSTRING(`membername`, 1, LOCATE(' ', `membername`) - 1),
        `membername`
    ),
    `memberlast` = IF(
        LOCATE(' ', `membername`) > 0,
        SUBSTRING(`membername`, LOCATE(' ', `membername`) + 1),
        NULL
    );

It seems that existing responses are over complicated or not a strict answer to the particular question.

I think, the simple answer is the following query:

SELECT
    SUBSTRING_INDEX(`membername`, ' ', 1) AS `memberfirst`,
    SUBSTRING_INDEX(`membername`, ' ', -1) AS `memberlast`
;

I think it is not necessary to deal with more-than-two-word names in this particular situation. If you want to do it properly, splitting can be very hard or even impossible in some cases:

• Johann Sebastian Bach
• Johann Wolfgang von Goethe
• Edgar Allan Poe
• Jakob Ludwig Felix Mendelssohn-Bartholdy
• Petőfi Sándor
• Virág Vendelné Farkas Margit
• 黒澤 明

In a properly designed database, human names should be stored both in parts and in whole. This is not always possible, of course.