Question

Using the function to split strings: http://blog.fedecarg.com/2009/02/22/mysql-split-string-function/

SELECT SUBSTRING_INDEX( SUBSTRING_INDEX( fullname,  ' ', 1 ) ,  ' ', -1 ) AS firstname,
SUBSTRING_INDEX( SUBSTRING_INDEX( fullname,  ' ', 2 ) ,  ' ', -1 ) AS lastname
FROM users;

I get the following resuts:

firstname | lastname |

    john      doe

    jane      doe

I have the following questions:

1.)How can I insert the values on columns that already exist under the same table?

2.)How can I insert the values on columns that don’t exist under the same table?

Of course, the two columns being firstname | lastname

Answer 1

To insert these values:

INSERT INTO users (firstname, lastname)
SELECT SUBSTRING_INDEX( SUBSTRING_INDEX( fullname,  ' ', 1 ) ,  ' ', -1 ) AS firstname,
SUBSTRING_INDEX( SUBSTRING_INDEX( fullname,  ' ', 2 ) ,  ' ', -1 ) AS lastname
FROM users;

To update existing values, for the same row:

update users
set firstname = SUBSTRING_INDEX( SUBSTRING_INDEX(fullname,  ' ', 1 ) ,  ' ', -1 ),
   lastname = SUBSTRING_INDEX( SUBSTRING_INDEX(fullname,  ' ', 2 ) ,  ' ', -1 ) 

To update existing values, but a different row:

update users users_a, users users_b
set users_b.firstname = SUBSTRING_INDEX( SUBSTRING_INDEX( users_a.fullname,  ' ', 1 ) ,  ' ', -1 ),
    users_b.lastname = SUBSTRING_INDEX( SUBSTRING_INDEX( users_a.fullname,  ' ', 2 ) ,  ' ', -1 ) 
where users_a.??? = users_b.??? /* join condition as appropriate */