SQL SELECT Statement
The SQL SELECT Statement
The SELECT statement is used to
select data from a table. The tabular result is stored in a result table
(called the result-set).
Syntax
SELECT column_name(s)FROM table_name |
Note:
SQL statements are not case sensitive. SELECT is the same as select.
SQL SELECT Example
To select the content of columns
named "LastName" and "FirstName", from the database table
called "Persons", use a SELECT statement like this:
SELECT LastName,FirstName FROM Persons |
The database table
"Persons":
|
LastName |
FirstName |
Address |
City |
|
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
|
Svendson |
Tove |
Borgvn 23 |
Sandnes |
|
Pettersen |
Kari |
Storgt 20 |
|
The result
|
LastName |
FirstName |
|
Hansen |
Ola |
|
Svendson |
Tove |
|
Pettersen |
Kari |
Select All Columns
To select all columns from the
"Persons" table, use a * symbol instead of column names, like
this:
SELECT * FROM Persons |
Result
|
LastName |
FirstName |
Address |
City |
|
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
|
Svendson |
Tove |
Borgvn 23 |
Sandnes |
|
Pettersen |
Kari |
Storgt 20 |
|
The Result Set
The result from a SQL query is
stored in a result-set. Most database software systems allow navigation of the
result set with programming functions, like: Move-To-First-Record,
Get-Record-Content, Move-To-Next-Record, etc.
Programming functions like these
are not a part of this tutorial. To learn about accessing data with function
calls, please visit our ADO
tutorial.
Semicolon after SQL Statements?
Semicolon is the standard way to
separate each SQL statement in database systems that allow more than one SQL
statement to be executed in the same call to the server.
Some SQL tutorials end each SQL statement
with a semicolon. Is this necessary? We are using MS Access and SQL Server 2000
and we do not have to put a semicolon after each SQL statement, but some
database programs force you to use it.
The SELECT DISTINCT Statement
The DISTINCT keyword is used to
return only distinct (different) values.
The SELECT statement returns
information from table columns. But what if we only want to select distinct
elements?
With SQL, all we need to do is to
add a DISTINCT keyword to the SELECT statement:
Syntax
SELECT DISTINCT column_name(s)FROM table_name |
Using the DISTINCT keyword
To select ALL values from the
column named "Company" we use a SELECT statement like this:
SELECT Company FROM Orders |
"Orders" table
|
Company |
OrderNumber |
|
Sega |
3412 |
|
W3Schools |
2312 |
|
Trio |
4678 |
|
W3Schools |
6798 |
Result
|
Company |
|
Sega |
|
W3Schools |
|
Trio |
|
W3Schools |
Note that "W3Schools" is
listed twice in the result-set.
To select only DIFFERENT values
from the column named "Company" we use a SELECT DISTINCT statement
like this:
SELECT DISTINCT Company FROM Orders |
Result:
|
Company |
|
Sega |
|
W3Schools |
|
Trio |
Now "W3Schools" is
listed only once in the result-set.