UPDATE
clause indicates which table is to be modified.
Example:
Change the benefits for the librarian Margaret Chapman from partial to
full with this statement:
UPDATE EMPLOYEE
SET BENEFITS = 'FULL'
WHERE EID = 103 ;
The value 'FULL'
is the change being made. It will replace the
current value 'PART'
listed in the BENEFITS column for Margaret
Chapman, whose employee ID number is 103. A change is made for all
records that satisfy the search condition; in this example, only one
row is updated.
Example: The finance analysis needs to include the effects of a 10% pay raise to all staff; i.e., to all employees whose RANK is STAFF.
Use this statement to update all staff salaries with the intended
raise:
UPDATE EMP_RAISE
SET SALARY = SALARY * 1.1
WHERE RANK = 'STAFF' ;
If a portion of the EMP_RAISE table looked like this before the update:
EID ENAME DEPT RANK BENEFITS SALARY 101 Aster, John A. MKT STAFF FULL 32000 102 Barrington, Kyle MGT DHEAD FULL 45000 103 Chapman, Margaret LIB STAFF PART 22000 104 Jackson, Herbert RND STAFF FULL 30000 105 Price, Stella FIN DHEAD FULL 42000 106 Sanchez, Carla MKT STAFF FULL 35000 107 Smith, Roberta RND STAFF PART 25000 |
It would look like this after the update operation:
EID ENAME DEPT RANK BENEFITS SALARY 101 Aster, John A. MKT STAFF FULL 35200 102 Barrington, Kyle MGT DHEAD FULL 45000 103 Chapman, Margaret LIB STAFF PART 24200 104 Jackson, Herbert RND STAFF FULL 33000 105 Price, Stella FIN DHEAD FULL 42000 106 Sanchez, Carla MKT STAFF FULL 38500 107 Smith, Roberta RND STAFF PART 27500 |
Notice that only the STAFF rows are changed to reflect the increase. DHEAD row salaries remain as they were. As a word of caution, it's easy to "accidentally" modify all rows in a table. Check your statement carefully before executing it.