Relational database-relational model R (U,D,DOM,F) parsing

Relational models can be formally represented as R (u,d,dom,f)

R: Relationship Name

D: domain of the attribute

DOM: Mapping relationships for attributes

F: Dependency Relationship

In the case of Table A (A1, A2,A3):

1, A is the relationship name (R).

2. If A1 is a number (2) type, then the domain of the attribute is between -99~99, which is the field of the A1 attribute (D).

3, if the A2 attribute is the identity, the domain can be "tutor" and "postgraduate", corresponding to the tutor and graduate students have a (list) domain, this correspondence is called Attribute Mapping Relationship (DOM).

4, in a table A1 is the primary key, if the A1 table satisfies 2NF, then there is a dependency relationship of F={a1-->a2,a1-->a3} (F).

Relational database-relational model R (U,D,DOM,F) parsing