small tweak for tessa

gistfile1.sql

UPDATE `tbl_name` SET
    `first_name` = IF(
        LOCATE(' ', `name`) > 0,
        SUBSTRING(`name`, 1, LOCATE(' ', `name`) - 1),
        `name`
    ),
    `last_name` = IF(
        LOCATE(' ', `name`) > 0,
        SUBSTRING_INDEX(`name`, ' ' - 1), /* Changed line */
        NULL
    );