Working with Sequencing

In TopLink, sequence numbers are artificial keys that uniquely identify the records in a table. When you define a sequence number field for a descriptor, TopLink automatically generates a new sequence number every time you insert a new record into the table.

Use the Sequencing area of a descriptor's Descriptor Info tab (see Figure 4-1) to specify sequencing information

Database tables often use a sequence number as the primary key. The TopLink Mapping editor can use the database's native support or a sequence table to maintain sequence numbers.

Tip: Oracle recommends using sequence numbers for primary keys because they are single, guaranteed, unique values.

Other data values may require composite primary keys to make up a unique value, which is less optimal. Additionally, non-artificial values may need to change, and this is not allowed for primary keys.