Update from

You can use the Update from statement to update tables of one table from another

for example you have a table Employee_old_table (employee_id,employee_name,employee_lname)
and e table employee_new_table (employee_id,employee_full_name,employee_first_name,employee_last_name)

to set the employee order.employee_full_name = employee.employee_name + ' ' + employee_lname

you can do this

update employee_full_name
set
employee_full_name = e.employee_name + ' ' + e.empoyee_lname,
employee_first_name = e.employee_name,
employee_last_name = e.employee_lname
from employee e
where e.employee_id = employee_id

instead of

update employee_full_name
set
employee_full_name = (select e.employee_name + ' ' + e.empoyee_lname from employee e where e.employee_id = employee_id),
employee_first_name = (select e.employee_name from employee e where e.employee_id = employee_id),
employee_last_name = (select e.employee_lname from employee e where e.employee_id = employee_id)