Relation Schema

Nested Relations

Relations extended by point (1) of The Object-Relational Model are sometimes called "nested relations''. In the nested-relational model, we allow attributes of relations to have a type that is not atomic: particularly, a type can be a relation schema. Thus, there is a convenient,

Default Values / Indexes

When we create or change tuples, we sometimes do not have values for all components. For instance, we mentioned in "Simple Table Declarations" Example 2 that when we add a column to a relation schema, the existing tuples do not have a known value, and it was

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