Use three columns as primary key : Primary Key « Table « Oracle PL/SQL Tutorial






  1. Oracle PL/SQL Tutorial
  2. Table
  3. Primary Key
SQL>
SQL> create table registrations
  2  ( attendee    NUMBER(4)
  3  , course      VARCHAR2(6)
  4  , begindate   DATE
  5  , evaluation  NUMBER(1)
  6  , constraint  R_PK        primary key (attendee,course,begindate)
  7  ) ;

Table created.

SQL>
SQL> insert into registrations values (2,'SQL',date '2009-04-12',4   );

1 row created.

SQL> insert into registrations values (14,'SQL',date '2009-04-12',5   );

1 row created.

SQL> insert into registrations values (6,'SQL',date '2009-04-12',4   );

1 row created.

SQL> insert into registrations values (11,'SQL',date '2009-04-12',2   );

1 row created.

SQL> insert into registrations values (8,'SQL',date '2009-10-04',NULL);

1 row created.

SQL> insert into registrations values (9,'SQL',date '2009-10-04',3   );

1 row created.

SQL> insert into registrations values (13,'SQL',date '2009-10-04',4   );

1 row created.

SQL> insert into registrations values (13,'SQL',date '2009-12-13',NULL);

1 row created.

SQL> insert into registrations values (6,'SQL',date '2009-12-13',NULL);

1 row created.

SQL> insert into registrations values (3,'OAU',date '2009-08-10',4   );

1 row created.

SQL>
SQL> select evaluation
  2  from   registrations
  3  where  attendee = 8
  4  order  by evaluation;

EVALUATION
----------


SQL>
SQL> drop table registrations;

Table dropped.








6.15.Primary Key
6.15.1.Create a table with primary key, VARCHAR type column and date type column with default value
6.15.2.Alter table to insert primary key
6.15.3.Use combined column as the primary key
6.15.4.Try to add two primary keys to one table
6.15.5.All columns as primary key
6.15.6.One to many using a primary-key and foreign-key relationship
6.15.7.One-to-one using a primary-key and foreign-key relationship
6.15.8.Use three columns as primary key