Session 1 - Databases-JUNE 2023.pdf

Different kind of DBMS
• Hierarchical DBMS, 60s
• Relation DBMS, RDBMS, 70s
• Object DBMS, 80s
• Object-relational DBMS, 90s
• Most databases today are RDBMS or Object-
relational DBMS

Relational Database Systems
• Started in the 70s at IBM by Cod
• Several implementations by companies like Oracle,
Sybase, Upright and Microsoft
• Highly optimized systems
• Proven and mature technology
• Several international standards
• Most systems today uses a RDBMS

Purpose
• Make storing of data and accessing of data easy
• RDBMS
• Roles: Admin, Developer, Architect
• Databases: Oracle, SQL Server, DB2, MySQL,
Postgres, SQLite

CODD’S RULE
• Each cell should have only one data: each data should be accessible
• Data shouldn’t be duplicated: Edit/delete is difficult because you
don’t know how many/where all the data are. Duplicate occupies
space

TYPES OF DATABASES ON PURPOSE
• OLTP: Online Transaction Processing – manage your day to day
business. Bulk of the operations here is CUD (Create, Update,
Delete), Less of Read
• OLAP: Online Analytical Processing – Almost all the operation
here is READ

DATABASE SERVER
DB1
DB2 DB2
Connecting to a DB:
1. Hostname [IPAddress]
2. Database name
3. Username
4. Password
User Management:
1. Admin
2. Multiple users with different
roles and permission

Developer Role
DB1
C: Create data: INSERT
R: Read Data: SELECT
U: Update the data: UPDATE
D: Delete existing data: DELETE

Architect Role
DB1
How many tables?
What kind of data they will have?
How many columns you need?
What should be the data type of each column?
Do we require to add any constraints?

EMPID ENAME EMAILID PHONENO
Integer Varchar(40) VARCHAR(30) CHAR(11)
..
Rohit Sharma
Table Name: EMPLOYEES
Datatypes:
1. Integer
2. Real
3. Date
4. Text /Char
Datatypes in MYSQL: https://www.w3schools.com/mysql/mysql_datatypes.asp

Relationships in Database
• 1: 1 – One attribute belongs only one other attribute, Email ID & Phone
Number
– Put all these attributes in same table
• 1: Many / Many to 1 – One attribute can have multiple other attribute,
Employee to Department
– Create 2 tables and Join them using Foreign Key relationship
• Many to Many – multiple values, Students and Subjects
– Create 3 tables, 1 each for 2 attributes and 3rd table for the relationship

EMPID ENAME EMAILID PHONENO DID
Integer Varchar(40) VARCHAR(30) CHAR(11)
101 Sachin 1
102 Rohit 3
Table Name: EMPLOYEES
DID DNAME DCODE
1 Sales C105
2 Product Dev
Table Name: DEPARTMENTS
Department 20 cols
# = 10
Dept tab = 200

• Students: DS, ML, PYTHON
• Subjects: DS- 45, ML – 25, Python - 40
ROLLNO STUDENT
2 ROHIT
SUBID SUBNAME FACULTY
1 DS
TID ROLLNO SUBID
1 1 1
2 2 1
3 1 2

Assignment – Get 5 ER Diagrams
• Airline Pilot Scheduling
• Retail Banking Operation
• ATM Operations
• Library Management Systems
• Hospital Management Systems
• Hotel Management Systems
Pick one of those and
convert into database
object

SELECT THE DATABASE
• MYSQL:
https://dev.mysql.com/downloads/mysql/
• POSTGRES:
https://www.postgresql.org/download/windows/

SERVER
ADMIN TOOL
COMMAND LINE ACCESS

17
Creating the Database
• Following two tasks must be completed:
– Create database structure
– Create tables that will hold end-user data

19
The Database Schema
• Authentication
– Process through which DBMS verifies that only
registered users are able to access database
– Log on to RDBMS using user ID and password
created by database administrator
• Schema
– Group of database objects—such as tables and
indexes—that are related to each other

20
Data Types
• Data type selection is usually dictated by nature of
data and by intended use
• Pay close attention to expected use of attributes for
sorting and data retrieval purposes

22
Creating Table Structures
• Use one line per column (attribute) definition
• Use spaces to line up attribute characteristics and
constraints
• Table and attribute names are capitalized
• NOT NULL specification
• UNIQUE specification

23
Creating Table Structures (continued)
• Primary key attributes contain both a NOT NULL and
a UNIQUE specification
• RDBMS will automatically enforce referential
integrity for foreign keys
• Command sequence ends with semicolon

24
SQL Constraints
• NOT NULL constraint
– Ensures that column does not accept nulls
• UNIQUE constraint
– Ensures that all values in column are unique
• DEFAULT constraint
– Assigns value to attribute when a new row is added to table
• CHECK constraint
– Validates data when attribute value is entered

25
SQL Indexes
• When primary key is declared, DBMS automatically creates unique
index
• Often need additional indexes
• Using CREATE INDEX command, SQL indexes can be created on
basis of any selected attribute
• Composite index
– Index based on two or more attributes
– Often used to prevent data duplication

26
Data Manipulation Commands
• Adding table rows
• Saving table changes
• Listing table rows
• Updating table rows
• Restoring table contents
• Deleting table rows
• Inserting table rows with a select subquery

27
Adding Table Rows
• INSERT
– Used to enter data into table
– Syntax:
• INSERT INTO columnname
VALUES (value1, value2, … , valuen);

28
Adding Table Rows (continued)
• When entering values, notice that:
– Row contents are entered between parentheses
– Character and date values are entered between apostrophes
– Numerical entries are not enclosed in apostrophes
– Attribute entries are separated by commas
– A value is required for each column
• Use NULL for unknown values

29
Saving Table Changes
• Changes made to table contents are not
physically saved on disk until, one of the
following occurs:
– Database is closed
– Program is closed
– COMMIT command is used
• Syntax:
– COMMIT [WORK];
• Will permanently save any changes made to any
table in the database

30
Listing Table Rows
• SELECT
– Used to list contents of table
– Syntax:
• SELECT columnlist
FROM tablename;
• Columnlist represents one or more
attributes, separated by commas
• Asterisk can be used as wildcard character
to list all attributes

31
Updating Table Rows
• UPDATE
– Modify data in a table
– Syntax:
• UPDATE tablename
SET columnname = expression [, columname = expression]
[WHERE conditionlist];
• If more than one attribute is to be updated in row,
separate corrections with commas

32
Restoring Table Contents
• ROLLBACK
– Used to restore database to its previous
condition
– Only applicable if COMMIT command has not
been used to permanently store changes in
database
• Syntax:
– ROLLBACK;
• COMMIT and ROLLBACK only work with data
manipulation commands that are used to
add, modify, or delete table rows

33
Deleting Table Rows
• DELETE
– Deletes a table row
– Syntax:
• DELETE FROM tablename
[WHERE conditionlist ];
• WHERE condition is optional
• If WHERE condition is not specified, all rows from
specified table will be deleted

34
Inserting Table Rows with a
Select Subquery
• INSERT
– Inserts multiple rows from another table
(source)
– Uses SELECT subquery
• Query that is embedded (or nested) inside
another query
• Executed first
– Syntax:
• INSERT INTO tablename SELECT columnlist
FROM tablename;

35
Selecting Rows with
Conditional Restrictions
• Select partial table contents by placing restrictions on
rows to be included in output
– Add conditional restrictions to SELECT statement,
using WHERE clause
• Syntax:
– SELECT columnlist
FROM tablelist
[ WHERE conditionlist ] ;

36
Selecting Rows with
Conditional Restrictions (continued)

37
Selecting Rows with
Conditional Restrictions (continued)

38
Arithmetic Operators:
The Rule of Precedence
• Perform operations within parentheses
• Perform power operations
• Perform multiplications and divisions
• Perform additions and subtractions

39
Arithmetic Operators:
The Rule of Precedence (continued)

40
Special Operators
• BETWEEN
– Used to check whether attribute value is within a
range
• IS NULL
– Used to check whether attribute value is null
• LIKE
– Used to check whether attribute value matches given
string pattern

41
Special Operators (continued)
• IN
– Used to check whether attribute value matches
any value within a value list
• EXISTS
– Used to check if subquery returns any rows

42
Advanced Data Definition Commands
• All changes in table structure are made by using
ALTER command
– Followed by keyword that produces specific
change
– Following three options are available:
• ADD
• MODIFY
• DROP

43
Changing a Column’s Data Type
• ALTER can be used to change data type
• Some RDBMSs (such as Oracle) do not permit
changes to data types unless column to be changed
is empty

44
Changing a Column’s Data Characteristics
• Use ALTER to change data characteristics
• If column to be changed already contains data,
changes in column’s characteristics are permitted if
those changes do not alter the data type

45
Adding a Column
• Use ALTER to add column
– Do not include the NOT NULL clause for new
column

46
Dropping a Column
• Use ALTER to drop column
– Some RDBMSs impose restrictions on the deletion
of an attribute

48
Copying Parts of Tables
• SQL permits copying contents of selected table
columns so that the data need not be reentered
manually into newly created table(s)
• First create the PART table structure
• Next add rows to new PART table using PRODUCT
table rows

49
Adding Primary and Foreign Key Designations
• When table is copied, integrity rules do not copy, so
primary and foreign keys need to be manually defined on
new table
• User ALTER TABLE command
– Syntax:
• ALTER TABLE tablename ADD
PRIMARY KEY(fieldname);
• For foreign key, use FOREIGN KEY in place of PRIMARY KEY

50
Deleting a Table from the Database
• DROP
– Deletes table from database
– Syntax:
• DROP TABLE tablename;

51
Advanced Select Queries
• SQL provides useful functions that can:
– Count
– Find minimum and maximum values
– Calculate averages
• SQL allows user to limit queries to only those entries
having no duplicates or entries whose duplicates may
be grouped

53
Aggregate Functions (continued)

54

55

56

60
Virtual Tables: Creating a View
• View is virtual table based on SELECT query
– Can contain columns, computed columns, aliases,
and aggregate functions from one or more tables
• Base tables are tables on which view is based
• Create view by using CREATE VIEW command

61
Virtual Tables: Creating a View
(continued)

62
Joining Database Tables
• Ability to combine (join) tables on common
attributes is most important distinction between
relational database and other databases
• Join is performed when data are retrieved from more
than one table at a time
• Join is generally composed of an equality comparison
between foreign key and primary key of related
tables

63
Joining Tables with an Alias
• Alias can be used to identify source table
• Any legal table name can be used as alias
• Add alias after table name in FROM clause
– FROM tablename alias

64
Summary
• SQL commands can be divided into two overall
categories:
– Data definition language commands
– Data manipulation language commands
• The ANSI standard data types are supported by all
RDBMS vendors in different ways
• Basic data definition commands allow you to create
tables, indexes, and views

65
Summary (continued)
• DML commands allow you to add, modify, and delete rows from tables
• The basic DML commands are SELECT, INSERT, UPDATE, DELETE,
COMMIT, and ROLLBACK
• INSERT command is used to add new rows to tables
• SELECT statement is main data retrieval command in SQL

66
Summary (continued)
• Many SQL constraints can be used with columns
• The column list represents one or more column
names separated by commas
• WHERE clause can be used with SELECT, UPDATE, and
DELETE statements to restrict rows affected by the
DDL command

67
Summary (continued)
• Aggregate functions
– Special functions that perform arithmetic
computations over a set of rows
• ORDER BY clause
– Used to sort output of SELECT statement
– Can sort by one or more columns and use either
an ascending or descending order
• Join output of multiple tables with SELECT statement

68
Summary (continued)
• Natural join uses join condition to match only rows
with equal values in specified columns
• Right outer join and left outer join used to select
rows that have no matching values in other related
table

69
Introduction to SQL
• SQL functions fit into two broad categories:
– Data definition language
• SQL includes commands to:
– Create database objects, such as tables, indexes, and views
– Define access rights to those database objects
– Data manipulation language
• Includes commands to insert, update, delete, and
retrieve data within database tables

The Relational Model
• All data is stored in tables with rows and columns
pnr* name surname sex
1 Fredrik Ålund Male
2 Eva Larsson Female

• Relations between tables and data
pnr* car
1 Volvo
pnr* name
1 Fredrik
2 Eva

• Each column contains atomic data
• Views is an alternative view of a table
• Normalization is used to make the data model as flexible
as possible
– No column should depend on any other column in the
row
– No redundant data
– Several levels of normalization and the third normal
form is the most used

Standardized Query Language, SQL
• SQL is a ISO standard supported by basically all
vendors, more or less
• SQL 92, SQL 99 and the new SQL 200x
• SQL is used to create the data model
• SQL is used to query the database
• SQL is used to perform updates
• Powerful language created to manipulate data

74
Objectives
• Explore basic commands and functions of SQL
• How to use SQL for data administration (to create
tables, indexes, and views)
• How to use SQL for data manipulation (to add,
modify, delete, and retrieve data)
• How to use SQL to query a database to extract useful
information

SQL Basics
• Tables can be created with the create command
– C REATE TABLE PERSON(pnr int, namn char(10), surname char(10), sex char(6))
– CREATE TABLE PERSON_CARS(pnr int, car char(7))
• Primary keys are defined in the create statement
– C REATE TABLE PERSON(pnr int, namn char(10), surname char(10), sex char(6),
primary key(pnr))

Online Free Editor for SQL
• https://livesql.oracle.com
• https://www.w3schools.com/sql/trysql.asp?filename
=trysql_op_in

SQL Basics
• Foreign keys can also be defined in the create statement
– CREATE TABLE PERSON_CARS(pnr int, car char(7),
foreign key(pnr) references PERSON(pnr) on delete
cascade)
On Delete Options:
Restrict : Nothing gonna be delete if there is a child row
Cascade : the child row will be delete / update too
Set Null : the child column will be set to null if you delete the parent
No action : The child row will not be concern of the delete / update

SQL Basics
• A column can have restrictions and default values
– CREATE TABLE PERSON(pnr int, name char(10)
default ‘Unknown’, surname char(10), sex char(6)
not null, primary key(pnr))

SQL Basics
• A table can be altered after has been created
– ALTER TABLE PERSON_CARS ADD CONSTRAINT
person_car_pk PRIMARY KEY(pnr, car)
– ALTER TABLE PERSON ADD COLUMN AGE INT

SQL Basics
• Data is retrieved with the SELECT statement
– SELECT * FROM PERSON
– SELECT PNR, NAME FROM PERSON
– SELECT * FROM PERSON WHERE AGE > 25 AND
SEX=‘Male’
• Tables are joined in the SELECT statement
– SELECT PERSON.NAME, PERSON_CARS.CAR FROM
PERSON, PERSON_CARS WHERE PERSON.PNR =
PERSON_CARS.PNR

SQL Basics
• Data is inserted with the INSERT statement
– INSERT INTO PERSON(pnr, name, surname,sex,
age) VALUES(3, ‘Eva’, ‘Larsson’, ‘Female’, ’27’)
– INSERT INTO PERSON_CARS(pnr, car)
VALUES(3,’Toyota’)

SQL Basics
• Data can be update with the UPDATE statements
– UPDATE PERSON SET AGE=22 WHERE PNR=1
• Update Fredriks age to 22
– UPDATE PERSON_CAR SET CAR=‘Volvo’
• Updates all cars to Volvo

SQL Basics
• Data is deleted with the DELETE statement
– DELETE FROM PERSON WHERE ID=3
• Deletes the row with Eva Larsson

SQL Basics
• Views are created with a combination of a CREATE and a
SELECT
– CREATE VIEW VOLVO_OWNERS(pnr, name, surname,
sex, age) as SELECT p.pnr, name, surname, sex, age
FROM PERSON p, PERSON_CARS pc WHERE
pc.pnr=p.pnr AND pc.cars=‘Volvo’
• Only show Volvo users
• SELECT * FROM VOLVO_OWNERS

Advanced SQL
• Stored Procedures
– A precompiled query in the database. Entire systems
can be built with Stored Procedures.
• Triggers
– Certain events can trigger actions, for example a
stored procedure might be started when a row is
deleted
• Both Stored Procedures and Triggers are part of SQL 99

Transactions
• Transactions is the way that the RDBMS keeps the
data consistent
– A transaction is supposed to have the ACID
property
• Atomic
• Consistent
• Isolated
• Durable

Transactions
• The classic example is the cash machine
– If the cash machine gives out the money, but the
reduce balance doesn’t finnish, we have too much
mony
– If the balance is reduced but we don’t get any
money we have too little

Transactions in SQL
• A transaction is started with START
• A transaction is commited with COMMIT
– If ok, everything is secured and well
• A transaction is rolled back (undone) with ROLLBACK
– All operations are undone

89
Introduction to SQL (continued)

90

91

• Assignment on SQL Programming

Session 1 - Databases-JUNE 2023.pdf

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