1. Database Architecture and Basic
Concepts
What is Database?
Structured Query Language
Stored Procedures
2. What is Database?
A database is an object for storing complex, structured
information.
What make database unique is the fact that databases are
design to retrieve data quickly.
Database samples such as Access and SQL Server called
database management systems (DBMS).
To access the data stored in the database and to update the
database, you use a special language, Structure Query
Language (SQL).
5. Structure Query Language
SQL (Structured Query Language) is a universal language for
manipulating tables, and every database management system
(DBMS) supports it.
SQL is a nonprocedural language.
SQL statements are categorized into two major categories:
Data Manipulation Language (DML)
Data Definition Language (DDL)
6. Continue…
Executing SQL Statements.
Opening Microsoft SQL Server Management Studio
Using New Query Windows.
7. Continue…
Selection Queries
The simplest form of the SELECT statement is
SELECT fields
FROM tables
where fields and tables are comma-separated lists of the fields you want
to retrieve from the database
and the tables they belong to.
8. WHERE Clause
To restrict the rows returned by the query, use the WHERE clause
of the SELECT statement. The most common form of the SELECT statement is
the following:
SELECT fields
FROM tables
WHERE condition
The fields and tables arguments are the same as before.
Sample:
SELECT ProductName, CategoryName
FROM Products
WHERE CategoryID In (2, 5,6,10)
9. TOP Keyword
Some queries may retrieve a large number of rows, while
you‟re interested in the top few rows only.
The TOP N keyword allows you to select the first N rows and
ignore the remaining ones.
DISTINCT Keyword
The DISTINCT keyword eliminates any duplicates from the
cursor retrieved by the SELECT statement.
SELECT DISTINCT Country
FROM Customers
10. ORDER Keyword
The rows of a query are not in any particular order. To request
that the rows be returned in a specific order, use the
ORDER BY clause, whose syntax is
ORDER BY col1, col2, . . .
SELECT CompanyName, ContactName
FROM Customers
ORDER BY Country, City
11. SQL Join
Joins specify how you connect multiple tables in a query, and there are four types
of joins:
Left outer, or left join
Right outer, or right join
Full outer, or full join
Inner join
Left Joins
This join displays all the records in the left table and only those records of the
table on the right that match certain user-supplied criteria. This join has the
following syntax:
FROM (primary table) LEFT JOIN (secondary table) ON (primary table).(field)
(comparison) (secondary table).(field)
SELECT title, pub_name
FROM titles LEFT JOIN publishers
ON titles.pub_id = publishers.pub_id
12. Right Joins
This join is similar to the left outer join, except that all rows in the table on the right
are displayed and only the matching rows from the left table are displayed. This join has
the following syntax:
FROM (secondary table) RIGHT JOIN (primary table) ON (secondary table).(field)
(comparison) (primary table).(field)
“SELECT title, pub_name
FROM titles RIGHT JOIN publishers
ON titles.pub_id = publishers.pub_id”
Full Joins
The full join returns all the rows of the two tables, regardless of whether there are
matching rows or not. In effect, it‟s a combination of left and right joins.
“SELECT title, pub_name
FROM titles FULL JOIN publishers
ON titles.pub_id = publishers.pub_id”
13. Inner Joins
This join returns the matching rows of both tables, similar to the WHERE clause, and has
the following syntax:
FROM (primary table) INNER JOIN (secondary table) ON (primary table).(field)
(comparison) (secondary table).(field)
“SELECT titles.title, publishers.pub_name FROM titles, publishers
WHERE titles.pub_id = publishers.pub_id”
Or
“SELECT titles.title, publishers.pub_name
FROM titles INNER JOIN publishers ON titles.pub_id =
publishers.pub_id”
14. Grouping Rows
Sometimes you need to group the results of a query, so that you
can calculate subtotals.
SELECT ProductID,
SUM(Quantity * UnitPrice *(1 - Discount))
AS [Total Revenues]
FROM [Order Details]
GROUP BY ProductID
ORDER BY ProductID
15. Action Queries
Execute queries that alter the data in the database‟s tables.
There are three types of actions you can perform against a database:
1. Insertions of new rows (INSERT)
2. Deletions of existing rows (DELETE)
3. Updates (edits) of existing rows (UPDATE)
Deleting Rows
The DELETE statement deletes one or more rows
from a table, and its syntax is:
DELETE table_name WHERE criteria
“DELETE Orders
WHERE OrderDate < „1/1/1998‟ ”
16. Inserting New Rows
The syntax of the INSERT statement is:
INSERT table_name (column_names) VALUES (values)
column_names and values are comma-separated lists of columns and their respective values.
“INSERT Customers (CustomerID, CompanyName) VALUES („FRYOG‟, „Fruit &
Yogurt‟)”
Or
“INSERT INTO SelectedProducts
SELECT * FROM Products WHERE CategoryID = 4”
17. Editing Existing Rows
The UPDATE statement edits a row‟s fields, and its syntax is
UPDATE table_name SET field1 = value1, field2 = value2,
… WHERE criteria
“UPDATE Customers SET Country=‟United Kingdom‟
WHERE Country = „UK‟ “
20. Stored Procedures
Stored procedures are short programs that are executed on the server and
perform very specific tasks.
Any action you perform against the database frequently should be coded
as a stored procedure, so that you can call it from within any application
or from different parts of the same application.
Benefit:
Stored procedures isolate programmers from the database and minimize the
risk of impairing the database‟s integrity.
You don‟t risk implementing the same operation in two different ways.
Using stored procedures is that they‟re compiled by SQL Server and they‟re
executed faster.
Stored procedures contain traditional programming statements that allow
you to validate arguments, use default argument values, and so on.
The language you use to write stored procedure is called T-SQL, and it‟s
a superset of SQL.
21. ALTER PROCEDURE dbo.SalesByCategory
@CategoryName nvarchar(15),
@OrdYear nvarchar(4) = „1998‟
AS
IF @OrdYear != „1996‟ AND @OrdYear != „1997‟ AND @OrdYear != „1998‟
BEGIN
SELECT @OrdYear = „1998‟
END
SELECT ProductName,
TotalPurchase = ROUND(SUM(CONVERT(decimal(14,2),
OD.Quantity * (1-OD.Discount) * OD.UnitPrice)), 0)
FROM [Order Details] OD, Orders O, Products P, Categories C
WHERE OD.OrderID = O.OrderID
AND OD.ProductID = P.ProductID
AND P.CategoryID = C.CategoryID
AND C.CategoryName = @CategoryName
AND SUBSTRING(CONVERT(nvarchar(22), O.OrderDate, 111), 1, 4) = @OrdYear
GROUP BY ProductName
ORDER BY ProductName
