EDIT: If the column doesn't yet exist you need to modify the table structure first, and then run the UPDATE below:
ALTER TABLE EMPLOYEE ADD COLUMN MIDDLENAME TEXT(25); -- or whatever length
The question isn't entirely clear to me, but it sounds like you're trying to update an existing employee by changing his middle name:
UPDATE EMPLOYEE
SET MIDDLENAME = 'JUNIOR'
WHERE EMPLOYEE_ID = 'E9876543';
You had a few syntax errors in your query:
EMPLOYEE_ID IS 'E9876543) ... use = and not IS
- () around your
WHERE clause
- Probably a misplaced
) in your string literal ... 'E9876543)'
Also, be careful about how you use the terms insert and update when it comes to database queries.