Beginning SQL

Chapter 12
As you can imagine, giving GRANT OPTION privileges to other users allows them unlimited ability to
pass on the privileges to other users, which can be very dangerous in some circumstances, particularly
for the UPDATE and DELETE privileges. You should use GRANT OPTION with discretion.
Revoking Privileges
If you’ve granted privileges that you need to revoke, you do so using the REVOKE statement. Revoking
privileges can yield unexpected results depending on the implementation used by your DBMS, whether
more than one user granted privileges on an object, and the time sequence of the grants. You see that in a
little while, but first you need to learn the REVOKE statement’s basic syntax.
The REVOKE Statement
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The REVOKE syntax looks very similar to the GRANT syntax. The REVOKE statement can take away some or
all of the privileges assigned in a GRANT statement, to some or all of the user IDs. For example, suppose
you granted some privileges on the Personnel table:
GRANT SELECT, UPDATE, INSERT
ON tblPersonnel
TO usrTom, usrJim
You can then use the following statement to revoke various INSERT privileges from Tom:
REVOKE INSERT
ON tblPersonnel
FROM usrTom
You can likewise revoke SELECT and INSERT privileges from Jim using this statement:
REVOKE SELECT, INSERT
ON tblPersonnel
FROM usrJim
Revoking UPDATE privileges from Jim and Tom requires a statement similar to the following:
REVOKE UPDATE
ON tblPersonnel
FROM usrJim, usrTom
You can revoke only privileges that you granted. If the user was granted privileges on the same object by
another user, only the privileges you granted are revoked. Thus, if the user you are revoking privileges
for was granted privileges on the same object by another user, they are still able to access that object
using any privileges that the other user gave them.
You grant Jim privileges on tblPersonnel with this statement:
GRANT SELECT, UPDATE, INSERT
ON tblPersonnel
TO usrJim