Guide to Oracle 10

Candidate Keys

• Guide to Oracle 10g

• Any column that could be used as the primary key
• Should be a column that is unique for each record and does not change

Surrogate Keys

• Guide to Oracle 10g

• Column created to be record’s primary key identifier
• Has no real relationship to row to which it is assigned other than to identify it uniquely
• Surrogate key values automatically generated using a sequence

Foreign Keys

• Guide to Oracle 10g

• Column in table that is a primary key in another table
• Creates relationship between two tables
• Value must exist in table where it is the primary key

Composite Keys

• Guide to Oracle 10g

• Unique key that is created by combining two or more columns
• Usually comprises fields that are primary keys in other tables

ORDER_ID	PRODUCT_ID	ORDER_QUANTITY
100	1	2
100	2	2
200	2	2
200	1	1

• Composite
• Key

Database Systems

• Guide to Oracle 10g

• Consists of
• DBMS
• Manages physical storage and data retrieval
• Database applications
• Provide interface that allows users to interact with database
• Server
• Computer that shares resources with other computers