Posted By

bbrumm on 07/27/17

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sql
Oracle

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Last Edited at 07/27/17 04:51am

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Primary Key and Foreign Key

/ Published in: SQL

A few examples of creating a primary key and a foreign key

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/* Primary Key */
CREATE TABLE employee (
employee_id NUMBER(10),
first_name VARCHAR2(100),
last_name VARCHAR2(100),
salary NUMBER(8),
department_id NUMBER(10),
CONSTRAINT employee_pk PRIMARY KEY (employee_id)
);
 
 
 
ALTER TABLE employee
ADD CONSTRAINT employee_pk PRIMARY KEY (employee_id);
 
 
 
ALTER TABLE employee DROP CONSTRAINT employee_pk;
 
ALTER TABLE employee DISABLE CONSTRAINT employee_pk;
 
 
ALTER TABLE employee ENABLE CONSTRAINT employee_pk;
 
/*Foreign key */
 
CREATE TABLE employee (
employee_id NUMBER(10),
first_name VARCHAR2(100),
last_name VARCHAR2(100),
salary NUMBER(8),
department_id NUMBER(10),
CONSTRAINT fk_emp_deptid FOREIGN KEY (department_id) REFERENCES department(department_id)
);
 
ALTER TABLE employee
ADD CONSTRAINT fk_emp_deptid FOREIGN KEY (department_id) REFERENCES department(department_id);
 
 
ALTER TABLE employee DROP CONSTRAINT fk_emp_deptid;
 
ALTER TABLE employee DISABLE CONSTRAINT fk_emp_deptid;
 
ALTER TABLE employee ENABLE CONSTRAINT fk_emp_deptid;