8.4.1. Ejemplos - Creando tablas

Las tablas son objetos en la base de datos que almacenan los datos de un usuario, organizados en filas y columnas, similar a una hoja de cálculo. Cada fila representa un registro único, mientras que cada columna corresponde a un campo dentro de ese registro.

Este concepto es fundamental en las bases de datos relacionales.

Sintaxis:

• CREATE TABLE [esquema.]Nombre-tabla (nombre-columna1 tipo-de-datos [DEFAULT valor] [ [CONSTRAINT “nombre-constraint”] clase-constraint [ENABLE / DISABLE]] (, nombre-columna2 tipo-datos [default valor] [ [CONSTRAINT “nombre-del-constraint”] clase-constraint [ENABLE / DISABLE]] [… [CONSTRAINT [nombre-constraint] clase-constraint [ENABLE / DISABLE]]),

Creación de restricciones, Unique, 1º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_ID NUMBER(4,0) UNIQUE),

2º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_ID NUMBER(4,0) CONSTRAINT DEPARTMENT_ID_UK UNIQUE ENABLE),

3º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_IDN NUMBER(4,0), CONSTRAINT DEPARTMENT_ID_UK UNIQUE (DEPARTMENT_ID) ENABLE),

Not null, 1º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_ID NUMBER(4,0) NOT NULL),

2º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT-ID NUMBER(4,0) CONSTRAINT DEPARTMENT-ID-NN NOT NULL ENABLE),

3º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_ID NUMBER(4,0), CONSTRAINT DEPARTMENT_ID_NN NOT NULL (DEPARTMENT_ID) ENABLE),

Primary key, 1º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_ID NUMBER(4,0) PRIMARY KEY),

2º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT-ID NUMBER(4,0) CONSTRAINT DEPARTMENT-ID-PK PRIMARY KEY ENABLE),

3º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_ID NUMBER(4,0), CONSTRAINT DEPARTMENT_ID_PK PRIMARY KEY (DEPARTMENT_ID) ENABLE),

Foreign key, 1º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_ID NUMBER(4,0), FOREIGN KEY (“DEPARTMENT_ID”) REFERENCES HR.EMPLOYEES(EMPLOYEE_ID) ENABLE),

2º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_ID NUMBER(4,0), CONSTRAINT DEPARTMENT_ID_FK FOREIGN KEY (DEPARTMENT_ID) REFERENCES HR.EMPLOYEES(EMPLOYEE_ID) ENABLE),

CHEK, 1º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_ID NUMBER(4,0) CHECK (DEPARTMENT_ID 1000),

2º Forma:

• CREATE TABLE HR.DEPARTMENTO (DEPARTMENT_ID NUM