Sql for biggner

SQL is an ANSI (American National Standards Institute)
standard computer language for accessing and
manipulating database systems. SQL statements are used
to retrieve and update data in a database. SQL works with
database programs like MS Access, DB2, Informix, MS SQL
Server, Oracle, Sybase, etc.
Unfortunately, there are many different versions of the
SQL language, but to be in compliance with the ANSI
standard, they must support the same major keywords in
a similar manner (such as SELECT, UPDATE, DELETE,
INSERT, WHERE, and others).
Note: Most of the SQL database programs also have their
own proprietary extensions in addition to the SQL
standard!
SQL is a Standard - BUT....

SQL Database Tables
A database most often contains one or more tables. Each table is
identified by a name (e.g. "Customers" or "Orders"). Tables contain
records (rows) with data.
Below is an example of a table called "Persons":
LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Svendson Tove Borgvn 23 Sandnes
Pettersen Kari Storgt 20 Stavanger

With SQL, we can query a database and have a result set returned.
A query like this:
SELECT LastName FROM Persons
Gives a result set like this:
SQL Queries
LastName
Hansen
Svendson
Pettersen

Difference between SQL server
2005 and 2008

SQL Server 2005 SQL Server 2008
XML data type is introduced.
XML data type is used.
Can not encrypt the entire
database.
Can encrypt the entire database
introduced in 2008.
Date time is used for both date
and time.
Date and time are separately
used for date and time
No table data type is included. Table data type introduced.
SSIS is started using. SSIS avails in this version.
CMS is not available. Central Management Server
(CMS) is Introduced.
PBM is not available Policy based management(PBM)
server is Introduced.

Data Types in SQL
 Characters:
 CHAR(20) -- fixed length
 VARCHAR(40) -- variable length
 Numbers:
 BIGINT, INT, SMALLINT, TINYINT
 REAL, FLOAT -- differ in precision
 MONEY
 Times and dates:
 DATE
 DATETIME -- SQL Server
 Others... All are simple
7

SQL Data Manipulation Language
(DML)
SQL (Structured Query Language) is a syntax for executing
queries. But the SQL language also includes a syntax to
update, insert, and delete records.
These query and update commands together form the Data
Manipulation Language (DML) part of SQL:
•SELECT - extracts data from a database table
•UPDATE - updates data in a database table
•DELETE - deletes data from a database table
•INSERT INTO - inserts new data into a database table

SQL Data Definition Language (DDL)
The Data Definition Language (DDL) part of SQL permits
database tables to be created or deleted. We can also define
indexes (keys), specify links between tables, and impose
constraints between database tables.
The most important DDL statements in SQL are:
•CREATE TABLE - creates a new database table
•ALTER TABLE - alters (changes) a database table
•DROP TABLE - deletes a database table
•CREATE INDEX - creates an index (search key)
•DROP INDEX - deletes an index

SQL The 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

To select the columns named "LastName" and "FirstName", use a SELECT
statement like this:
SELECT LastName, FirstName FROM Persons
Persons
výsledok
LastName FirstName
Hansen Ola
Svendson Tove
Pettersen Kari

To select all columns from the "Persons" table, use a * symbol instead of
column names, like this:
SELECT * FROM Persons
Select All Columns

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.
The Result Set

Eliminating Duplicates
15
SELECT DISTINCT category
FROM Product
Compare to:
SELECT category
FROM Product
Category
Gadgets
Gadgets
Photography
Household
Category
Gadgets
Photography
Household

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
The SELECT DISTINCT Statement

To select ALL values from the column named "Company" we use a SELECT
statement like this:
SELECT Company FROM Orders
Orders
Company OrderNumber
Sega 3412
W3Schools 2312
Trio 4678
W3Schools 6798
Company
Sega
W3Schools
Trio
W3Schools
Using the DISTINCT keyword

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
Company
Sega
W3Schools
Trio
Orders
Company OrderNumber
Sega 3412
W3Schools 2312
Trio 4678
W3Schools 6798

Select All Columns
The WHERE clause is used to specify a selection criterion.
The WHERE Clause
To conditionally select data from a table, a WHERE clause can be added to the
SELECT statement.
Syntax
SELECT column FROM table
WHERE column operator value

With the WHERE clause, the following operators can be used:
Operator Description
= Equal
<> Not equal
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
BETWEEN Between an inclusive range
LIKE Search for a pattern
Note: In some versions of SQL the <> operator may be written as !=

Using the WHERE Clause
To select only the persons living in the city "Sandnes", we add a WHERE clause to
the SELECT statement:
WHERE City='Sandnes'
LastName FirstName Address City Year
Hansen Ola Timoteivn 10 Sandnes 1951
Svendson Tove Borgvn 23 Sandnes 1978
Svendson Stale Kaivn 18 Sandnes 1980
Pettersen Kari Storgt 20 Stavanger 1960
LastName FirstName Address City Year
Hansen Ola Timoteivn 10 Sandnes 1951
Svendson Tove Borgvn 23 Sandnes 1978
Svendson Stale Kaivn 18 Sandnes 1980

Ordering the Results
22
SELECT pname, price, manufacturer
FROM Product
WHERE category=‘gizmo’ AND price > 50
ORDER BY price, pname
Ordering is ascending, unless you specify the DESC keyword.
Ties are broken by the second attribute on the ORDER BY list, etc.

23
SELECT category
FROM Product
ORDER BY pname
PName Price Category Manufacturer
Gizmo $19.99 Gadgets GizmoWorks
Powergizmo $29.99 Gadgets GizmoWorks
SingleTouch $149.99 Photography Canon
MultiTouch $203.99 Household Hitachi
?

24
SELECT DISTINCT category
FROM Product
ORDER BY category
Compare to:
Category
Gadgets
Household
Photography
SELECT category
FROM Product
ORDER BY pname ?

Joins in SQL
 Connect two or more tables:
25
Product
Company Cname StockPrice Country
GizmoWorks 25 USA
Canon 65 Japan
Hitachi 15 Japan
What is
the connection
between
them ?

Joins
26
Product (pname, price, category, manufacturer)
Company (cname, stockPrice, country)
Find all products under $200 manufactured in Japan;
return their names and prices.
SELECT pname, price
FROM Product, Company
WHERE manufacturer=cname AND country=‘Japan’
AND price <= 200
Join
between Product
and Company

Joins in SQL
27
Product
Company
Cname StockPrice Country
GizmoWorks 25 USA
Canon 65 Japan
Hitachi 15 Japan
PName Price
SingleTouch $149.99
SELECT pname, price
WHERE manufacturer=cname AND country=‘Japan’
AND price <= 200

Joins
28
Company (cname, stockPrice, country)
Find all countries that manufacture some product in the ‘Gadgets’
category.
SELECT country
WHERE manufacturer=cname AND category=‘Gadgets’

Joins in SQL
29
Name Price Category Manufacturer
Product
Company
GizmoWorks 25 USA
Canon 65 Japan
Hitachi 15 Japan
SELECT country
Country
??
??
What is
the problem ?
What’s the
solution ?

Joins
30
Purchase (buyer, seller, store, product)
Person(persname, phoneNumber, city)
Find names of people living in Seattle that bought some product in the
‘Gadgets’ category, and the names of the stores they bought such
product from
SELECT DISTINCT persname, store
FROM Person, Purchase, Product
WHERE persname=buyer AND product = pname AND
city=‘Seattle’ AND category=‘Gadgets’

Joins in SQL
31
Name Price Category Manufacturer
Product
Company
GizmoWorks 25 USA
Canon 65 Japan
Hitachi 15 Japan
SELECT country
Country
??
??
What is
the problem ?
What’s the
solution ?

Joins
32
Find names of people living in Seattle that bought some product in the
‘Gadgets’ category, and the names of the stores they bought such
product from
SELECT DISTINCT persname, store
FROM Person, Purchase, Product
WHERE persname=buyer AND product = pname AND
city=‘Seattle’ AND category=‘Gadgets’

When are two tables related?
 You guess they are
 I tell you so
 Foreign keys are a method for schema designers to
tell you so (7.1)
 A foreign key states that a column is a reference to the
key of another table
ex: Product.manufacturer is foreign key of Company
 Gives information and enforces constraint
33

Disambiguating Attributes
 Sometimes two relations have the same attr:
Person(pname, address, worksfor)
Company(cname, address)
34
SELECT DISTINCT pname, address
FROM Person, Company
WHERE worksfor = cname
SELECT DISTINCT Person.pname, Company.address
FROM Person, Company
WHERE Person.worksfor = Company.cname
Which
address ?

Tuple Variables
35
SELECT DISTINCT x.store
FROM Purchase AS x, Purchase AS y
WHERE x.product = y.product AND y.store = ‘BestBuy’
Find all stores that sold at least one product that the store
‘BestBuy’ also sold:
Answer (store)

Tuple Variables
36
General rule:
tuple variables introduced automatically by the system:
Product (name, price, category, manufacturer)
Becomes:
Doesn’t work when Product occurs more than once:
In that case the user needs to define variables explicitly.
SELECT name
FROM Product
WHERE price > 100
SELECT Product.name
FROM Product AS Product
WHERE Product.price > 100

Using Quotes
Note that we have used single quotes around the conditional values in the
examples.
SQL uses single quotes around text values (most database systems will also
accept double quotes). Numeric values should not be enclosed in quotes.
For text values:
This is correct:
SELECT * FROM Persons WHERE FirstName='Tove'
This is wrong:
SELECT * FROM Persons WHERE FirstName=Tove

The LIKE Condition
The LIKE condition is used to specify a search for a pattern in a column.
Syntax
SELECT column FROM table
WHERE column LIKE pattern
A "%" sign can be used to define wildcards (missing letters in the pattern)
both before and after the pattern.

Using LIKE
The following SQL statement will return persons with first names that start with
an 'O':
WHERE FirstName LIKE 'O%'
The following SQL statement will return persons with first names that end with
an 'a':
WHERE FirstName LIKE '%a'

Using LIKE 2
The following SQL statement will return persons with first names that contain the
pattern 'la':
WHERE FirstName LIKE '%la%'

The INSERT INTO Statement
The INSERT INTO statement is used to insert new rows into a table.
Syntax
INSERT INTO table_name
VALUES (value1, value2,....)
You can also specify the columns for which you want to insert data:
INSERT INTO table_name (column1, column2,...)
VALUES (value1, value2,....)

Insert a New Row
And this SQL statement:
INSERT INTO Persons
VALUES ('Hetland', 'Camilla', 'Hagabakka 24', 'Sandnes')
Hetland Camilla Hagabakka 24 Sandnes

Insert Data in Specified ColumnsLastName FirstName Address City
And This SQL statement:
INSERT INTO Persons (LastName, Address)
VALUES ('Rasmussen', 'Storgt 67')
Rasmussen Storgt 67

The Update Statement
The UPDATE statement is used to modify the data in a table.
Syntax
UPDATE table_name
SET column_name = new_value
WHERE column_name = some_value

Update one Column in a Row
Nilsen Fred Kirkegt 56 Stavanger
Rasmussen Storgt 67
We want to add a first name to the person with a last name of "Rasmussen":
UPDATE Person SET FirstName = 'Nina'
WHERE LastName = 'Rasmussen'
Rasmussen Nina Storgt 67

Update several Columns in a Row
We want to change the address and add the name of the city:
UPDATE Person
SET Address = 'Stien 12', City = 'Stavanger'
WHERE LastName = 'Rasmussen'
Rasmussen Nina Stien 12 Stavanger
Rasmussen Storgt 67

The Delete Statement
The DELETE statement is used to delete rows in a table.
Syntax
DELETE FROM table_name
WHERE column_name = some_value

Delete a RowLastName FirstName Address City
"Nina Rasmussen" is going to be deleted:
DELETE FROM Person WHERE LastName = 'Rasmussen'

Delete All RowsIt is possible to delete all rows in a table without deleting the table. This means
that the table structure, attributes, and indexes will be intact:
DELETE FROM table_name
Or
DELETE * FROM table_name

Exercises
54
Company (cname, stock price, country)
Person(per-name, phone number, city)
Ex #1: Find people who bought telephony products.
Ex #2: Find names of people who bought American products
Ex #3: Find names of people who bought American products and they
live in Seattle.
Ex #4: Find people who have both bought and sold something.
Ex #5: Find people who bought stuff from Joe or bought products
from a company whose stock prices is more than $50.

Sql for biggner

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