## Access Control

• Object can be a Table or a View
• Privileges can be
• Select
• Insert
• Delete
• References (cols) – allow to create a foreign key that references the specifies column(s)
• All
• Can later be REVOKEd
• Users can be single users or groups

### Integrity Constraints

• Every legal instance of a relation must satisfy ICs.
• Types of IC’s: Domain constraints, prmary key constraints, foreign key constraints, general consraints
• Domain constraints: Field values must be of right type
• Primary key and foreign key constrains:

### Keys

• A set of fields is a superkey if
• No two distinct tuples can have same values in all key fields
• A set of files is a key for a relation if it is minimal:
• It is a superkey
• No subset of the fields is a superkey
• One of keys is chosen to be primary key.
• Other keys are called candidate keys.
• Specify candidate keys using UNIQUE

## General Constraints

• Create constraints using CHECK
• Name constraints using CONSTRAINT