Databases Reference
In-Depth Information
fIGure 11.3
Compound Instance Key.
Instance Key value for the last row is 32; if the entity B has 862 rows, the
Instance Key value for the first row is 1 and the Instance Key value for the
last row is 862. When joining to a table with a Compound Instance Key,
likewise with any table having a compound key, the join must include the
Entity Key and the Instance Key, because the combination of the Entity
Key and Instance Key is required to uniquely identify an individual row.
Join to a simple Instance key
A join to a Simple Instance Key is achieved by embedding the Instance
Key value as a foreign key. The example in Figure 11.4 shows a Transaction
table that joins to a dimension table named Item. That join is achieved
