Explain how linkages between relational tables are accomplished.
What will be an ideal response?
Tables that are logically related in the data model need to be physically linked. The degree of association between the tables (i.e., 1:1, 1:M, or M:M) determines how the linking occurs. The key-assignment rules for linking tables are discussed below. Where a true 1:1 association exists between tables, either (or both) primary keys may be embedded as foreign keys in the related table.
Where a 1:M (or 1:0,M) association exists, the primary key of the 1 side is embedded in the table of the M side.
To represent the M:M association between tables, a link table needs to be created that has a combined (composite) key consisting of the primary keys of two related tables.
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