Grant/Revoke Privileges

Grant Privileges on Tables

You can grant users various privileges to tables. These privileges can be any combination of select, insert, update, delete, references, alter, and index. Below is an explanation of what each privilege means.

Privilege	Description
Select	Ability to query the table with a select statement.
Insert	Ability to add new rows to the table with the insert statement.
Update	Ability to update rows in the table with the update statement.
Delete	Ability to delete rows from the table with the delete statement.
References	Ability to create a constraint that refers to the table.
Alter	Ability to change the table definition with the alter table statement.
Index	Ability to create an index on the table with the create index statement.

The syntax for granting privileges on a table is:

grant privileges on object to user;

For example, if you wanted to grant select, insert, update, and delete privileges on a table called suppliers to a user name smithj, you would execute the following statement:

grant select, insert, update, delete on suppliers to smithj;

You can also use the all keyword to indicate that you wish all permissions to be granted. For example:

grant all on suppliers to smithj;

If you wanted to grant select access on your table to all users, you could grant the privileges to the public keyword. For example:

grant select on suppliers to public;

Revoke Privileges on Tables

Once you have granted privileges, you may need to revoke some or all of these privileges. To do this, you can execute a revoke command. You can revoke any combination of select, insert, update, delete, references, alter, and index.
The syntax for revoking privileges on a table is:

revoke privileges on object from user;

For example, if you wanted to revoke delete privileges on a table called suppliers from a user named anderson, you would execute the following statement:

revoke delete on suppliers from anderson;

If you wanted to revoke all privileges on a table, you could use the all keyword. For example:

revoke all on suppliers from anderson;

If you had granted privileges to public (all users) and you wanted to revoke these privileges, you could execute the following statement:

revoke all on suppliers from public;

Grant Privileges on Functions/Procedures

When dealing with functions and procedures, you can grant users the ability to execute these functions and procedures. The Execute privilege is explained below:

Privilege	Description
Execute	Ability to compile the function/procedure. Ability to execute the function/procedure directly.

The syntax for granting execute privileges on a function/procedure is:

grant execute on object to user;

For example, if you had a function called Find_Value and you wanted to grant execute access to the user named smithj, you would execute the following statement:

grant execute on Find_Value to smithj;

If you wanted to grant all users the ability to execute this function, you would execute the following:

grant execute on Find_Value to public;

Revoke Privileges on Functions/Procedures

Once you have granted execute privileges on a function or procedure, you may need to revoke these privileges from a user. To do this, you can execute a revoke command.
The syntax for the revoking privileges on a function or procedure is:

revoke execute on object from user;

If you wanted to revoke execute privileges on a function called Find_Value from a user named anderson, you would execute the following statement:

revoke execute on Find_Value from anderson;

If you had granted privileges to public (all users) and you wanted to revoke these privileges, you could execute the following statement:

revoke execute on Find_Value from public;

Data Control Language (DCL) Statements

Data Control Language Statements are used to grant privileges on tables, views, sequences, synonyms, procedures to other users or roles.

The DCL statements are

GRANT          :Use to grant privileges to other users or roles.

REVOKE       :Use to take back privileges granted to other users and roles.

Privileges are of two types :

• System Privileges
• Object privileges

System Privileges are normally granted by a DBA to users. Examples of system privileges are CREATE SESSION, CREATE TABLE, CREATE USER etc.

Object privileges means privileges on objects such as tables, views, synonyms, procedure. These are granted by owner of the object.

Object Privileges are

ALTER	Change the table definition with the ALTER TABLE statement.
DELETE	Remove rows from the table with the DELETE statement. Note: You must grant the SELECT privilege on the table along with the DELETE privilege.
INDEX	Create an index on the table with the CREATE INDEX statement.
INSERT	Add new rows to the table with the INSERT statement.
REFERENCES	Create a constraint that refers to the table. You cannot grant this privilege to a role.
SELECT	Query the table with the SELECT statement.
UPDATE	Change data in the table with the UPDATE statement.
	Note: You must grant the SELECT privilege on the table along with the UPDATE privilege.

Grant

Grant is use to grant privileges on tables, view, procedure to other users or roles

Examples

Suppose you own emp table. Now you want to grant select,update,insert privilege on this table to other user “SAMI”.

 

grant select, update, insert on emp to sami;

Suppose you want to grant all privileges on emp table to sami. Then

grant  all on emp to sami;

Suppose you want to grant select privilege on emp to all other users of the database. Then

grant select on emp to public;

Suppose you want to grant update and insert privilege on only certain columns not on all the columns then include the column names in grant statement. For example you want to grant update privilege on ename column only and insert privilege on empno and ename columns only. Then give the following statement

grant update (ename),insert (empno, ename)  on emp to sami;

To grant select statement on emp table to sami and to make sami be able further pass on this privilege you have to give WITH GRANT OPTION clause in GRANT statement like this.

grant select on emp to sami with grant option;

REVOKE

Use to revoke privileges already granted to other users.

For example to revoke select, update, insert privilege you have granted to Sami then give the following statement.

revoke select, update, insert on emp from sami;

To revoke select statement on emp granted to public give the following command.

revoke select on emp from public;

To revoke update privilege on ename column and insert privilege on empno and ename columns give the following revoke statement.

revoke update, insert on emp from sami;

Note :You cannot take back column level privileges. Suppose you just want to take back  insert privilege on ename column then you have to first take back the whole insert privilege and then grant privilege on empno column.

ROLES

A role is a group of Privileges. A role is very handy in managing privileges, Particularly in such situation when number of users should have the same set of privileges.

 

 

For example you have four users :Sami, Scott, Ashi, Tanya in the database. To these users you want to grant select ,update privilege on emp table, select,delete privilege on dept table. To do this first create a role by giving the following statement

 

create role clerks

 

Then grant privileges to this role.

 

grant select,update on emp to clerks;

grant select,delete on dept to clerks;

 

Now grant this clerks role to users like this

 

grant clerks to sami, scott, ashi, tanya ;

 

Now Sami, Scott, Ashi and Tanya have all the privileges granted on clerks role.

 

Suppose after one month you want grant delete on privilege on emp table all these users then just grant this privilege to clerks role and automatically all the users will have the privilege.

 

grant delete on emp to clerks;

 

If you want to take back update privilege on emp table from these users just take it back from clerks role.

 

revoke update on emp from clerks;

 

 

To Drop a role

 

Drop role clerks;

 

LISTING INFORMATION ABOUT PRIVILEGES

 

To see which table privileges are granted by you to other users.

 

SELECT * FROM USER_TAB_PRIVS_MADE

 

To see which table privileges are granted to you by other users

 

SELECT * FROM USER_TAB_PRIVS_RECD;

 

To see which column level privileges are granted by you to other users.

 

SELECT * FROM USER_COL_PRIVS_MADE

 

To see which column level privileges are granted to you by other users

 

SELECT * FROM USER_COL_PRIVS_RECD;

 

To see which privileges are granted to roles

 

SELECT * FROM USER_ROLE_PRIVS;