SWE4004 S4 The Relational Model

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SWE4004 S4 The Relational Model by Mind Map: SWE4004 S4 The Relational Model

1. Purpose and advantages of views.

2. In each tuple of R, values of K uniquely identify that tuple (uniqueness).

3. Alternative Terminology for Relational Model

4. An attribute, or set of attributes, that uniquely identifies a tuple within a relation.

5. Order of attributes has no significance.

6. Each tuple is distinct; there are no duplicate tuples.

7. Values of an attribute are all from the same domain.

7.1. Order of tuples has no significance, theoretically.

8. Relation name is distinct from all other relation names in relational schema.

9. Each attribute has a distinct name.

10. Each cell of relation contains exactly one atomic (single) value.

11. Objectives

11.1. Terminology of relational model.

11.2. How tables are used to represent data.

11.3. Connection between mathematical relations and relations in the relational model.

11.4. Properties of database relations.

11.5. Meaning of entity integrity and referential integrity.

11.6. How to identify CK, PK, and FKs.

12. Terminology

12.1. A relation is a table with columns and rows.

12.1.1. Only applies to logical structure of the database, not the physical structure.

12.2. Attribute is a named column of a relation.

12.3. Domain is the set of allowable values for one or more attributes.

12.4. Tuple is a row of a relation.

12.5. Degree is the number of attributes in a relation.

12.6. Cardinality is the number of tuples in a relation.

12.7. Instances of Branch and Staff Relations

12.8. Relational Database is a collection of normalized relations with distinct relation names.


12.10. Examples of Attribute Domains

13. Properties of Relations

14. Relational Keys

14.1. Superkey

14.2. Superkey (K) such that no proper subset is a superkey within the relation.

14.3. Candidate Key

14.3.1. No proper subset of K has the uniqueness property (irreducibility

14.4. Primary Key

14.4.1. Candidate key selected to identify tuples uniquely within relation.

14.5. Alternate Keys

14.5.1. Candidate keys that are not selected to be primary key.

14.6. Foreign Key

14.6.1. Represents value for an attribute that is currently unknown or not applicable for tuple.

14.6.2. Attribute, or set of attributes, within one relation that matches candidate key of some (possibly same) relation.

15. Integrity Constraints

15.1. Null

15.1.1. Deals with incomplete or exceptional data.

15.1.2. Represents the absence of a value and is not the same as zero or spaces, which are values

15.2. Referential Integrity

15.2.1. If foreign key exists in a relation, either foreign key value must match a candidate key value of some tuple in its home relation or foreign key value must be wholly null.

15.3. Entity Integrity

15.3.1. In a base relation, no attribute of a primary key can be null.

15.4. General Constraints

15.4.1. Additional rules specified by users or database administrators that define or constrain some aspect of the enterprise.