Slide 14.10: The SELECT statement (cont.)

Slide 14.9: The SELECT statement
Slide 14.11: The WHERE clause
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The SELECT Statement (Cont.)

The SELECT DISTINCT Statement
The DISTINCT keyword is used to return only distinct (different) values. Note that “W3Schools” is listed twice in the result-set if the keyword DISTINCT is not used. To select only DIFFERENT values from the column named Company we use a SELECT DISTINCT statement.

 SQL> create table  Orders (
   2    Company      varchar(32),
   3    OrderNumber  Number(4) );

 Table created.

 SQL> insert into  Orders  values ('Sega', 3412);

 1 row created.

 SQL> insert into  Orders  values ('W3Schools', 2312);

 1 row created.

 SQL> insert into  Orders  values ('Trio', 4678);

 1 row created.

 SQL> insert into  Orders  values ('W3Schools', 6798);

 1 row created.


 SQL> select  Company  from  Orders;

 COMPANY
 --------------------------------
 Sega
 W3Schools
 Trio
 W3Schools


 SQL> select distinct  Company  from  Orders;

 COMPANY
 --------------------------------
 Sega
 Trio
 W3Schools

The following is an SQL test area from w3schools.com where the Customers table may be created by the following command:

   SQL> create table  Customers (
     2    CustomerID   varchar(16),
     3    CompanyName  varchar(32),
     4    ContactName  varchar(32),
     5    Address      varchar(64),
     6    City         varchar(32),
     7    PostalCode   varchar(16),
     8    Country      varchar(32) );

Note that the Customers table is for read only.