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Wednesday, October 26, 2011

SQL SELECT Statement

This chapter will explain the SELECT and the SELECT * statements.

The SQL SELECT Statement

The SELECT statement is used to select data from a database.
The result is stored in a result table, called the result-set.

SQL SELECT Syntax

SELECT column_name(s)
FROM table_name
and
SELECT * FROM table_name
Note Note: SQL is not case sensitive. SELECT is the same as select.

An SQL SELECT Example

The "Persons" table:
P_Id LastName FirstName Address City
1 Hansen Ola Timoteivn 10 Sandnes
2 Svendson Tove Borgvn 23 Sandnes
3 Pettersen Kari Storgt 20 Stavanger
Now we want to select the content of the columns named "LastName" and "FirstName" from the table above.
We use the following SELECT statement:
SELECT LastName,FirstName FROM Persons
The result-set will look like this:
LastName FirstName
Hansen Ola
Svendson Tove
Pettersen Kari


SELECT * Example

Now we want to select all the columns from the "Persons" table.
We use the following SELECT statement:
SELECT * FROM Persons
Tip: The asterisk (*) is a quick way of selecting all columns!
The result-set will look like this:
P_Id LastName FirstName Address City
1 Hansen Ola Timoteivn 10 Sandnes
2 Svendson Tove Borgvn 23 Sandnes
3 Pettersen Kari Storgt 20 Stavanger


Navigation in a Result-set

Most database software systems allow navigation in 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 or our PHP tutorial.