Basic SQL Queries:
We use the default database of northwind to explain the 'Basic Queries of SQL'.You can download northwind database from: Download
Learn How to Attach .mdf File of database
A
SELECT indicates that we are merely reading information, as opposed to
modifying it. What where selecting is identified by an expression or column
list immediately following the SELECT. The FROM statement specifies the name of
the table or tables from which we are getting our data.
Syntax:
SELECT <column list>
[FROM <source table(s)>]
Example 1
Select
* from Employees;
The above query Selects
all the employees records from the data base and displays its columns.
Example 2
Select
FirstName, LastName from Employees;
The above query Selects
data of these two columns from the Employees table
Then
there are some functions that can be used in select statement syntax is
Syntax:
SELECT function(<column list>)
[FROM <source table(s)>]
Function
are SUM, COUNT, DISTINCT, AVG, MIN and MAX there are many other function that
are also available.
Example 3
SELECT
CustomerID, EmployeeID, COUNT(*)
FROM
Orders;
Syntax:
SELECT function(<column list>)
[FROM <source table(s)>]
[WHERE]<condition>]
The WHERE clause immediately
follows the
FROM
clause and defines what conditions a record has to meet before it will be
shown.
Example 4
SELECT
Name, ProductNumber, ReorderPoint
FROM
Production.Product
WHERE
ProductID = 356
1- Get
Order id, product id, unit price from Order Details.
select OrderID,ProductID,UnitPrice from dbo.[Order
Details];
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2-
Count
total number of employees.
select COUNT(EmployeeID)AS Number from Employees;
3-
Get the most expensive product amount from Products.
select Max (UnitPrice) from dbo.Products
4- Multiply unit price to quantity in OrderDetails
to get OrderPrice.
select UnitPrice * Quantity AS
OrderPrice from dbo.[Order
Details];
5- Display all cities that employees belong to but don’t
allow repetition.
select Distinct City from
dbo.Employees
6-
Display the complete name of all the employees.
select FirstName+LastName As
CompleteName from dbo.Employees
7-
Display data of all employees those working as Sales Representative.
select * from dbo.Employees where
Title = 'Sales
Representative';
8-
Display the CustomerID of customers whose order is shipped to London and
display the column name as CustomerID_London.
select CustomerID
As CustomerID_London from
dbo.Customers
where City =
'London'
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