Replace spaces
UPDATE `table` SET `col_name` = REPLACE(`col_name`, ' ', '')
Remove all tabs characters
UPDATE `table` SET `col_name` = REPLACE(`col_name`, '\t', '' )
Remove all new line characters
UPDATE `table` SET `col_name` = REPLACE(`col_name`, '\n', '')
http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_replace
Remove first and last space(s) of column
UPDATE `table` SET `col_name` = TRIM(`col_name`)
http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_trim