Oracle PL/SQL Tutorial/Table/Primary Key

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All columns as primary key

   <source lang="sql">

SQL> SQL> create table keywords

 2  ( word  varchar2(50),
 3    position   int,
 4    doc_id int,
 5    primary key(word,position,doc_id)
 6  );

Table created. SQL> SQL> drop table keywords; Table dropped.</source>


Alter table to insert primary key

   <source lang="sql">

SQL> CREATE TABLE department (

 2  dept_id           INTEGER,
 3  dept_name     VARCHAR2(32));

SQL> SQL> ALTER TABLE department

 2  ADD CONSTRAINT pk_dept PRIMARY KEY (dept_id);

Table altered.

SQL> SQL> drop table department; Table dropped.</source>


Create a table with primary key, VARCHAR type column and date type column with default value

   <source lang="sql">

CREATE TABLE myTable (

 2    id INTEGER PRIMARY KEY,
 3    status VARCHAR2(10),
 4    last_modified DATE DEFAULT SYSDATE
 5  );

Table created. SQL> SQL> desc myTable;

Name              Null?    Type
ID                NOT NULL NUMBER(38)
STATUS                     VARCHAR2(10)
LAST_MODIFIED                                                                                                                                                                  DATE

SQL> SQL> drop table myTable; Table dropped.</source>


One to many using a primary-key and foreign-key relationship

   <source lang="sql">

SQL> SQL> SQL> CREATE TABLE Programmer

 2     (lect_id    VARCHAR2(10) NOT NULL,
 3      lect_name  VARCHAR2(20),
 4      PRIMARY KEY (lect_id));

Table created. SQL> SQL> CREATE TABLE Course

 2     (course_id        VARCHAR2(10) NOT NULL,
 3      course_name      VARCHAR2(20),
 4      lect_id          VARCHAR(10),
 5      PRIMARY KEY (course_id),
 6      FOREIGN KEY (lect_id) REFERENCES Programmer (lect_id)
 7      ON DELETE CASCADE);

Table created. SQL> SQL> drop table Programmer cascade constraints; Table dropped. SQL> drop table Course cascade constraints; Table dropped.</source>


One-to-one using a primary-key and foreign-key relationship

   <source lang="sql">

SQL> SQL> SQL> CREATE TABLE Office

 2     (office_id        VARCHAR2(10) NOT NULL,
 3      building_name    VARCHAR2(20),
 4      PRIMARY KEY (office_id));

Table created. SQL> SQL> CREATE TABLE Programmer

 2     (lect_id    VARCHAR2(10) NOT NULL,
 3      lect_name  VARCHAR2(20),
 4      office_id  VARCHAR2(10),
 5      PRIMARY KEY (lect_id),
 6      FOREIGN KEY (office_id) REFERENCES Office (office_id)
 7      ON DELETE CASCADE);

Table created. SQL> SQL> drop table Office cascade constraints; Table dropped. SQL> drop table Programmer cascade constraints; Table dropped.</source>


Try to add two primary keys to one table

   <source lang="sql">

SQL> SQL> -- create demo table SQL> create table Employee(

 2    ID                 VARCHAR2(4 BYTE)         NOT NULL primary key,
 3    First_Name         VARCHAR2(10 BYTE),
 4    Last_Name          VARCHAR2(10 BYTE),
 5    Start_Date         DATE,
 6    End_Date           DATE,
 7    Salary             Number(8,2),
 8    City               VARCHAR2(10 BYTE),
 9    Description        VARCHAR2(15 BYTE)
10  )
11  /

Table created. SQL> SQL> -- prepare data SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)

 2               values ("01","Jason",    "Martin",  to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto",  "Programmer")
 3  /

1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)

 2                values("02","Alison",   "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester")
 3  /

1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)

 2                values("03","James",    "Smith",   to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester")
 3  /

1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)

 2                values("04","Celia",    "Rice",    to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager")
 3  /

1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)

 2                values("05","Robert",   "Black",   to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
 3  /

1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)

 2                values("06","Linda",    "Green",   to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York",  "Tester")
 3  /

1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)

 2                values("07","David",    "Larry",   to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York",  "Manager")
 3  /

1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)

 2                values("08","James",    "Cat",     to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester")
 3  /

1 row created. SQL> SQL> SQL> SQL> -- display data in the table SQL> select * from Employee

 2  /

ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION


-------------------- -------------------- --------- --------- ---------- ---------- ---------------

01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer 02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver Tester 03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver Tester 04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager 05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester 06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York Tester 07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York Manager

ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION


-------------------- -------------------- --------- --------- ---------- ---------- ---------------

08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver Tester 8 rows selected. SQL> SQL> alter table employee

 2  add constraint emp_pk
 3  primary key( id );

primary key( id )

ERROR at line 3: ORA-02260: table can have only one primary key

SQL> SQL> desc employee;

Name            Null?    Type

ID              NOT NULL VARCHAR2(4)
FIRST_NAME               VARCHAR2(10)
LAST_NAME                VARCHAR2(10)
START_DATE               DATE
END_DATE                 DATE
SALARY                   NUMBER(8,2)
CITY                     VARCHAR2(10)
DESCRIPTION              VARCHAR2(15)

SQL> SQL> SQL> SQL> -- clean the table SQL> drop table Employee

 2  /

Table dropped.</source>


Use combined column as the primary key

   <source lang="sql">

SQL> SQL> create table myTable(

 2  id               number(6) not null,
 3  salary           number(8,2),
 4  hire_date        date default sysdate,
 5  termination_date date,
 6  termination_desc varchar2(4000),
 7  constraint       emphistory_pk primary key (id, hire_date)
 8  );

Table created. SQL> SQL> describe myTable;

Name                  Null?    Type

ID                    NOT NULL NUMBER(6)
SALARY                         NUMBER(8,2)
HIRE_DATE             NOT NULL DATE
TERMINATION_DATE               DATE
TERMINATION_DESC               VARCHAR2(4000)

SQL> SQL> SQL> drop table myTable; Table dropped.</source>


Use three columns as primary key

   <source lang="sql">

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.</source>