THE RELATIONAL DATA MODEL

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THE RELATIONAL DATA MODEL by Mind Map: THE RELATIONAL DATA MODEL

1. TYPES OF RELATIONSHIP

1.1. 1:M RELATIONSHIP

1.1.1. Should be norm in any relational database design

1.2. 1:1 RELATIONSHIP

1.2.1. Should be rare in any relational database design

1.3. M:N RELATIONSHIP

1.3.1. Cannot be implemented as such in the relational model

1.3.2. Relationship can be changed into 1:M relationship

2. CHARATERISTICS OF TABLE

2.1. : two-dimensional structure composed of rows and columns

2.2. each table row(tuple) represent a single entity occurence within the entity set

2.3. each table coloumn represent an attribute and each coloumn has a distinct name

2.4. each coloumn represent a single data value

3. KEYS

3.1. Composite key

3.1.1. Composed of more than one attriburte

3.2. Key attribute

3.2.1. Any attribute that is part of a key

3.3. Superkey

3.3.1. Any key that uniqeuly identifies each row

3.4. Candidate Key

3.4.1. A superkey without unecessary attributes

4. INTERGRITY RULES

4.1. ENTITY INTERGRITY

4.1.1. All primary key entries are unique and cannot be nul

4.1.2. Foreign key value refer to primary key value

4.2. REFERENCE INTERGRITY

4.2.1. Foreign key can be null and must refer to existing primary key

5. Relational Set Operators

5.1. Natural Join

5.1.1. Links tables by selecting rows with common values in common attribute(s

5.2. Equijoin

5.2.1. Links tables on the basis of an equality condition that compares specified columns

5.3. Theta join

5.3.1. Any other comparison operator is used

5.4. Outer join

5.4.1. Matched pairs are retained, and any unmatched values in other table are left null