THE RELATIONAL DATA MODEL

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

1. INTEGRITY RULES

1.1. many RDBMs enforce integrity rules automatically

1.2. safer to ensure application design conforms to entity and referential integrity rules

1.3. designers use flags to avoid nulls

2. RELATIONAL MODEL

2.1. relational data management system (RDBMS)

2.1.1. performs same functional provided by hierarchical model

2.1.2. hides complexity from the user

2.2. relational diagram

2.2.1. representation of entities,attributes and relationships

2.3. relational table stores collection of related entities

3. TABLE

3.1. The two-dimensional structure composed of raws and columns

3.2. contains group of related entities = an entity set

4. APPLICATION OF THE INTEGRITY RULES

4.1. safer to ensure application design conforms to entity and referential integrity rules

4.2. designers use flags to avoid nulls

5. KEYS

5.1. COMPOSITE KEY

5.1.1. COMPOSITE OF MORE THAN ONE ATTRIBUTE

5.2. KEY ATTRIBUTE

5.2.1. ANY ATTRIBUTE THAT IS PART OF A KEY

5.3. SUPERKEY

5.3.1. ANY KEY THAT UNIQUELY IDENTIFY EACH ROW

5.4. CANDIDATE KEY

5.4.1. A SUPERKEY WITHOUT UNNECESSARY ATTRIBUTE

5.5. FOREIGN KEY

5.5.1. AN ATTRIBUTE WHOSE VALUES MATCH PRIMARY KEY VALUES IN THE RELATED TABLE

5.6. REFERENTIAL INTEGRITY

5.6.1. fk CONTAINS A VALUE THAT REFERS TO AN EXISTING VALID TUPLE (ROW) IN ANOTHER RELATION

5.7. SECONDARY KEY

5.7.1. KEY USED STRICTLY FOR DATA RETRIEVAL PURPOSE

6. RELATIONSHIP

6.1. one entity related to only one other entity and vice versa

6.2. sometimes means that entity components were not defined properly

6.3. could indicate that two entities actually belong in the same table

6.4. certain condition absolutely require their use

7. INDEXES

7.1. INDEX KEY

7.1.1. index's reference point

7.1.2. points of data location identified by the key

7.2. UNIQUE INDEX

7.2.1. index in which the index key can have only one pointer value (row) associated with it

8. DATA DICTIONARY AND SYSTEM CATALOG

8.1. DATA DICTIONARY

8.1.1. provides details accounting of all tables found within the user/designer-created database

8.1.2. contain (at least) all the attributes names and characteristics for each table in the system

8.1.3. contain meta data

8.2. SYSTEM CATALOG

8.2.1. the detailed system data dictionary that describes all objects with the database