Referential Constraints : Foreign Key « Constraints « SQL Server / T-SQL Tutorial

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SQL Server / T-SQL Tutorial » Constraints » Foreign Key 
7. 3. 7. Referential Constraints
4>
5CREATE TABLE department(
6>    dept_no CHAR(4NOT NULL,
7>    dept_name CHAR(25NOT NULL,
8>    location CHAR(30NULL,
9>    CONSTRAINT prim_dept PRIMARY KEY (dept_no))
10> GO
1>
2CREATE TABLE employee (
3>            emp_no INTEGER NOT NULL,
4>            emp_fname CHAR(20NOT NULL,
5>            emp_lname CHAR(20NOT NULL,
6>            dept_no CHAR(4NULL,
7>            CONSTRAINT prim_emp PRIMARY KEY (emp_no),
8>            CONSTRAINT foreign_emp FOREIGN KEY(dept_noREFERENCES
9>       department(dept_no))
10> GO
1>
2CREATE TABLE project (project_no CHAR(4NOT NULL,
3>            project_name CHAR(15NOT NULL,
4>            budget FLOAT NULL,
5>            CONSTRAINT prim_proj PRIMARY KEY (project_no))
6> GO
1>
2CREATE TABLE myProject (emp_no INTEGER NOT NULL,
3>        project_no CHAR(4NOT NULL,
4>        job CHAR (15NULL,
5>        enter_date DATETIME NULL,
6>        CONSTRAINT prim_works PRIMARY KEY(emp_no, project_no),
7>        CONSTRAINT foreign1_works FOREIGN KEY(emp_noREFERENCES
8>        employee(emp_no),
9>        CONSTRAINT foreign2_works FOREIGN KEY(project_noREFERENCES
10>        project(project_no))
11> GO
1>
2> drop table myProject;
3> GO
1>
2> drop table project;
3> GO
1> drop table employee;
2> GO
1> drop table department;
2> GO
7. 3. Foreign Key
7. 3. 1. The FOREIGN KEY Clause
7. 3. 2. FOREIGN KEY Constraints
7. 3. 3. A statement that adds a foreign key constraint
7. 3. 4. ON DELETE and ON UPDATE Options
7. 3. 5. Adding a FOREIGN KEY to the Employees Table
7. 3. 6. Re-creating the FOREIGN KEY with NO ACTION (Implicitly)
7. 3. 7. Referential Constraints
7. 3. 8. Cascading Updates and Deletes
7. 3. 9. Supporting Basic Referential Integrity with Foreign Keys
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