VB.NET tutorial: SQL

SQL (Structured Query Language)

To be able to work with data of the database, it is important to gain basic knowledge of SQL language. In this part, we introduce you the basic sql statements commonly used. In this instruction, we use Tablename to refer to the table and fieldname to refer to the field of the table that we will work with.

Retrieve data from a table


SELECT * FROM Tablename;
Example:
SELECT * FROM Products;

Retrieve data from a table with sorting


SELECT * FROM Tablename
Order by fieldname Asc/Desc;
 
Example:
SELECT * FROM Products
Order By ProductID DESC;

Retrieve data from a table with condition


SELECT * FROM Tablename
Where condition;
 
Example:
SELECT * FROM Products
Where UnitPrice Between 20 And 30;
SELECT * FROM Products
Where UnitPrice>20 And UnitsOnOrder>20;

 

Retrieve data from multiple tables


SELECT Tablename1.fieldname1, Tablename1.fieldname2, Tablename2.fieldname1,
Tablename2.fieldname2
FROM Tablename1, Tablename2
Where how these tables are related
 
Example:
SELECT Products.ProductName,Products.UnitPrice,Products.UnitsInStock, Categories.CategoryName
FROM Products,Categories
Where Products.CategoryID=Categories.CategoryID;

Insert data into a table


INSERT INTO Tablename Values(val1,val2,value3..)
 
Example:
INSERT INTO Student_tbl Values('Stu006','Rithy Vansak');

Insert data into a table by specifying field names


INSERT INTO Tablename(fieldname1, fieldname 2,..)
Values(val1,val2,value3..)

Example:
INSERT INTO Student_tbl(StuID,StuName) Values('Stu007','Rithy Vansak');

Update data in a table


UPDATE TableName
SET fieldname 1=val1, fieldname 2=val2,f2…
Where condition

Example:
UPDATE Student_tbl
Set StuName='Rithy Chan'
Where StudID='Stu007';

Delete data from a table


-DELETE FROM Tblname Where condition;

Example:
DELETE FROM Student WHERE StuID='Stu007'

Note: For DELETE and UPDATE statements, you should set conditions(s). If you don’t set condition(s), all of your data in a specified table will be deleted or updated.





Comments

Name:
Comment:
Enter the text:
CAPTCHA image

....................................................................................................................Home | Forum | About | Contact
This website intents to provide free and high quality tutorials, examples, exercises and solutions, questions and answers of programming and scripting languages:
C, C++, C#, Java, VB.NET, Python, VBA,PHP & Mysql, SQL, JSP, ASP.NET,HTML, CSS, JQuery, JavaScript and other applications such as MS Excel, MS Access, and MS Word. However, we don't guarantee all things of the web are accurate. If you find any error, please report it then we will take actions to correct it as soon as possible.
Copyright @ 2011-2013 worldbestlearningcenter. All Rights Reserved.
Home Programming Web DB & App Questions Exercises Tips Programs FAQs Download About
Computer-Wbest
Popular Pages
You might like