Het belang van normaliseren van data

PostgreSQL-databases maken

Darryl Reeves

Industry Assistant Professor, New York University

Voorbeeld 1: redundante data

CREATE TABLE loan (
    borrower_id INTEGER REFERENCES borrower(id),
    bank_name VARCHAR(50) DEFAULT NULL,
    ...
);

CREATE TABLE bank ( 
    id SERIAL PRIMARY KEY, 
    name VARCHAR(50) DEFAULT NULL, 
    ... 
);

CREATE TABLE loan (
    borrower_id INTEGER REFERENCES borrower(id),
    bank_name VARCHAR(50) DEFAULT NULL,
    ...
);

CREATE TABLE bank ( 
    id SERIAL PRIMARY KEY, 
    name VARCHAR(50) DEFAULT NULL, 
    ... 
);

CREATE TABLE loan (
    borrower_id INTEGER REFERENCES borrower(id),
    bank_id INTEGER REFERENCES bank(id),
    ...
);

applicant

borrower

applicant

borrower

applicant

borrower

applicant

id	name
1	Jane Simmmons
2	Rick Demps

borrower

CREATE TABLE borrower (
    id SERIAL PRIMARY KEY,
    name VARCHAR(50) NOT NULL
);

CREATE TABLE borrower (
    id SERIAL PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    approved BOOLEAN DEFAULT NULL
);

PostgreSQL-databases maken