Oracle PL/SQL Tutorial/Query Select/DISTINCT

Displaying Distinct Rows

You can suppress the display of duplicate rows using the DISTINCT keyword.

SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL,
  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
08   James      Cat        17-SEP-96 15-APR-02    1232.78 Vancouver  Tester
8 rows selected.
SQL>
SQL>
SQL> SELECT Description FROM employee
  2  /
DESCRIPTION
---------------
Programmer
Tester
Tester
Manager
Tester
Tester
Manager
Tester
8 rows selected.
SQL> SELECT DISTINCT Description FROM employee
  2  /
DESCRIPTION
---------------
Programmer
Manager
Tester
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /
Table dropped.
SQL>

Select distinct column and other columns

SQL>
SQL>
SQL> CREATE TABLE employees (
  2    au_id    CHAR(3)     NOT NULL,
  3    au_fname VARCHAR(15) NOT NULL,
  4    au_lname VARCHAR(15) NOT NULL,
  5    phone    VARCHAR(12) NULL    ,
  6    address  VARCHAR(20) NULL    ,
  7    city     VARCHAR(15) NULL    ,
  8    state    CHAR(2)     NULL    ,
  9    zip      CHAR(5)     NULL
 10  );
Table created.
SQL>
SQL> INSERT INTO employees VALUES("A01","S","B","111-111-1111","75 St","Boston","NY","11111");
1 row created.
SQL> INSERT INTO employees VALUES("A02","W","H","222-222-2222","2922 Rd","Boston","CO","22222");
1 row created.
SQL> INSERT INTO employees VALUES("A03","H","H","333-333-3333","3800 Ave, #14F","San Francisco","CA","33333");
1 row created.
SQL> INSERT INTO employees VALUES("A04","K","H","444-444-4444","3800 Ave, #14F","San Francisco","CA","44444");
1 row created.
SQL> INSERT INTO employees VALUES("A05","C","K","555-555-5555","114 St","New York","NY","55555");
1 row created.
SQL> INSERT INTO employees VALUES("A06"," ","K","666-666-666","390 Mall","Palo Alto","CA","66666");
1 row created.
SQL> INSERT INTO employees VALUES("A07","P","O","777-777-7777","1442 St","Sarasota","FL","77777");
1 row created.
SQL>
SQL>
SQL> SELECT DISTINCT city, state
  2    FROM employees;
CITY            ST
--------------- --
San Francisco   CA
Palo Alto       CA
Sarasota        FL
New York        NY
Boston          NY
Boston          CO
6 rows selected.
SQL>
SQL>
SQL> drop table employees;
Table dropped.

Select distinct value

SQL>
SQL> CREATE TABLE employees (
  2    au_id    CHAR(3)     NOT NULL,
  3    au_fname VARCHAR(15) NOT NULL,
  4    au_lname VARCHAR(15) NOT NULL,
  5    phone    VARCHAR(12) NULL    ,
  6    address  VARCHAR(20) NULL    ,
  7    city     VARCHAR(15) NULL    ,
  8    state    CHAR(2)     NULL    ,
  9    zip      CHAR(5)     NULL
 10  );
Table created.
SQL>
SQL> INSERT INTO employees VALUES("A01","S","B","111-111-1111","75 St","Boston","NY","11111");
1 row created.
SQL> INSERT INTO employees VALUES("A02","W","H","222-222-2222","2922 Rd","Boston","CO","22222");
1 row created.
SQL> INSERT INTO employees VALUES("A03","H","H","333-333-3333","3800 Ave, #14F","San Francisco","CA","33333");
1 row created.
SQL> INSERT INTO employees VALUES("A04","K","H","444-444-4444","3800 Ave, #14F","San Francisco","CA","44444");
1 row created.
SQL> INSERT INTO employees VALUES("A05","C","K","555-555-5555","114 St","New York","NY","55555");
1 row created.
SQL> INSERT INTO employees VALUES("A06"," ","K","666-666-666","390 Mall","Palo Alto","CA","66666");
1 row created.
SQL> INSERT INTO employees VALUES("A07","P","O","777-777-7777","1442 St","Sarasota","FL","77777");
1 row created.
SQL>
SQL>
SQL> SELECT DISTINCT state
  2    FROM employees;
ST
--
CA
NY
CO
FL
SQL>
SQL>
SQL> drop table employees;
Table dropped.