1:a normalformen

Skapa PostgreSQL-databaser

Darryl Reeves

Industry Assistant Professor, New York University

Exempel: hantera elevregister

CREATE TABLE student (
    id SERIAL PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    courses VARCHAR(50) NOT NULL,
    home_room SMALLINT NOT NULL
);

Uppdateringsfel
Insättningsfel
Raderingsfel

Exempel: duplicerade data efter uppdatering

id	name	courses	home_room
122	Susan Roth	Algebra I, Physics, Spanish II	101
413	Robert Cruz	History, Geometry, Biology	204
613	Thomas Wright	English III, Chemistry, Algebra II	102

Exempel: duplicerade data efter uppdatering

id	name	courses	home_room
122	Susan Roth	Algebra I, Chemistry, Spanish II	101
413	Robert Cruz	History, Geometry, Biology	204
613	Thomas Wright	English III, Chemistry, Algebra II	102

Exempel: duplicerade data efter uppdatering

id	name	courses	home_room
122	Susan Roth	Algebra I, Chemistry, Spanish II, Chemistry	101
413	Robert Cruz	History, Geometry, Biology	204
613	Thomas Wright	English III, Chemistry, Algebra II	102

Exempel: insättningar med kolumnbegränsningar

CREATE TABLE student (
    id SERIAL PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    courses VARCHAR(50) NOT NULL,
    home_room SMALLINT NOT NULL
);

id	name	courses	home_room
122	Susan Roth	Algebra I, Physics, Spanish II	101
413	Robert Cruz	History, Geometry, Biology	204
613	Thomas Wright	English III, Chemistry, Algebra II	102

Exempel: insättningar med kolumnbegränsningar

CREATE TABLE student (
    id SERIAL PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    courses VARCHAR(50) NOT NULL,
    home_room SMALLINT NOT NULL
);

id	name	courses	home_room
122	Susan Roth	Algebra I, Physics, Spanish II	101
413	Robert Cruz	History, Geometry, Biology, French Literature	204
613	Thomas Wright	English III, Chemistry, Algebra II	102

Exempel: dataintegritet påverkas vid radering av poster

id	name	courses	home_room
122	Susan Roth	Algebra I, Physics, Spanish II	101
413	Robert Cruz	History, Geometry, Biology	204
613	Thomas Wright	English III, Chemistry, Algebra II	102

Exempel: dataintegritet påverkas vid radering av poster

id	name	courses	home_room
122	Susan Roth	Algebra I, Physics, Spanish II	101
413	Robert Cruz	History, Geometry, Biology	204
613	Thomas Wright	???	102

Uppfylla 1:a normalformen (1NF)

Krav för 1NF:
- Tabellvärden måste vara atomära

Exempel: elevertabell som uppfyller 1NF

CREATE TABLE student (
    id SERIAL PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    courses VARCHAR(50) NOT NULL,
    home_room SMALLINT NOT NULL
);

Exempel: elevertabell som uppfyller 1NF

CREATE TABLE student (
    id INTEGER,
    name VARCHAR(50) NOT NULL,
    courses VARCHAR(50) NOT NULL,
    home_room SMALLINT NOT NULL
);

Exempel: elevertabell som uppfyller 1NF

CREATE TABLE student (
    id INTEGER,
    name VARCHAR(50) NOT NULL,
    course VARCHAR(50) NOT NULL,
    home_room SMALLINT NOT NULL
);

Exempel: elevertabell som uppfyller 1NF

id	name	course	home_room
122	Susan Roth	Algebra I	101
122	Susan Roth	Physics	101
122	Susan Roth	Spanish II	101
413	Robert Cruz	History	204
413	Robert Cruz	Geometry	204
413	Robert Cruz	Biology	204

Exempel: elevertabell som uppfyller 1NF

CREATE TABLE student (
    id INTEGER,
    name VARCHAR(50) NOT NULL,
    course VARCHAR(50) NOT NULL,
    home_room SMALLINT NOT NULL
);

Exempel: elevertabell som uppfyller 1NF

CREATE TABLE student (
    student_id INTEGER,
    first_name VARCHAR(50) NOT NULL,
    last_name VARCHAR(50) NOT NULL,
    course VARCHAR(50) NOT NULL,
    home_room SMALLINT NOT NULL
);

Exempel: elevertabell som uppfyller 1NF

id	first_name	last_name	course	home_room
122	Susan	Roth	Algebra I	101
122	Susan	Roth	Physics	101
122	Susan	Roth	Spanish II	101
413	Robert	Cruz	History	204
413	Robert	Cruz	Geometry	204
413	Robert	Cruz	Biology	204

Nu kör vi en övning!

Skapa PostgreSQL-databaser