DBMS Chapter 3 Flashcards
Table (Informal)
Relation (Formal)
Column (Informal)
Attribute/Domain (Formal)
Row (Informal)
Tuple (Formal)
Values in a Column (Informal)
Domain (Formal)
Populated Table (informal)
Extension (Formal)
Sets
A set is any well-defined list, collection, or class of objects.
Subsets
If every element in a set A is also a member of a set B, then A is called a subset of B.
Union
The union of sets A and B is the set of all elements which belong to A or to B or to both. A∪B
Relation
A table of values (a set of rows, or set of columns)
Strength of Relational Approach
Comes from the formal foundation provided by the theory of relations
Tuple
An ordered set of values
Domain
An atomic set of values
Constraints (Definition)
Conditions that must hold on all valid relation instances
3 Relational Integrity Constraints
- Key Constraints 2. Entity Integrity Constraints 3. Referential Integrity Constraints
Key Constraint
Super Key, Candidate Key, Primary Key
Entity Integrity
The primary key attributes PK of each relation schema R in S cannot have null values in any tuple of r(R).
Referential Integrity
Used to specify a relationship among tuples in two relations
Converting ERD to relational schema
Update Operations on Relations
- INSERT a tuple.
- DELETE a tuple.
- MODIFY a tuple.
