Merge multiple rows together
You need to create a temporary table with the merged data, then remove the old table and then rename the temporary table with the correct table name.

EXAMPLE:

CREATE TABLE table_temp SELECT user,is_su,last_login,GROUP_CONCAT(roles-for_groups) AS roles-for_groups FROM table1 GROUP BY user;


Check if table_temp is ok and then you can remove your old table.

DROP TABLE table1


The last step, rename the new/temporary table to the actual table name

RENAME TABLE table_temp TO table1;


PS: I'm assuming your table name is table1 because you never posted the name.