The three main paradigms of SQL

First, a paradigm:

Must have a primary key, the column is not divided.

Ii. the second paradigm:

When a table is a composite primary key, the non-primary key field does not depend on the partial primary key,

For example:

CREATE TABLE SCI (

Sno Int (+), CNO Int (+), Grade int (+), credit int (32),

Primary KEY Sno,cno

)

Non-keyword attribute credit only functions depend on CNO, that is, the credit portion relies on the combination keyword (SNO,CNO) instead of full dependency.

Divided into two relational patterns SC1 (Sno,cno,grade), C2 (Cno,credit).

Iii. Third Paradigm:

All non-primary properties in relational mode R (u,f) do not have transitive dependencies on any candidate keywords

Example----S1 (Sno,sname,dno, dname, location)

The keyword SNO determines the location function by passing the dependency SNO-to location. In other words, Sno does not directly determine the location of the non-primary attribute.

Workaround: Divided into two relations S (Sno,sname,dno), D (dno,dname,location)

The three main paradigms of SQL