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Database part3-

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Taymoor Nazmy

1) The document describes an entity-relationship (ER) diagram for a university database. It identifies the main entities as Department, Course, Module, Lecturer, and Student. 2) The key relationships are that a Department offers multiple Courses, a Course includes multiple Modules, a Lecturer teaches multiple Modules, and a Student enrolls in a Course and takes the Modules required to complete it. 3) The document explains the different components of an ER diagram, including entities, relationships, attributes, keys, and relationship types (one-to-one, one-to-many, many-to-many). It provides examples of how to map an ER diagram to database tables.

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Course code: ITI131 Course title : Database PART: 3 Prof. Taymoor Mohamed Nazmy Dept. of computer science, faculty of computer science, Ain Shams uni. Ex-vice dean of post graduate studies and research Cairo, Egypt 1
Database design & E/R model 2
Steps for Creating Database
4 Database Design Data Modeling Refinement/ Normalization SQL Tables E/R diagrams Relations Files
Steps in Database Design • Requirements Analysis – user needs; what must database do? • Conceptual Design – high level description (often done w/ER model) • Logical Design – translate ER into DBMS data model • Schema Refinement – consistency, normalization • Physical Design - indexes, disk layout • Security Design - who accesses what, and how 5
6 Entity Relation (ER) Diagram  1976 proposed by Peter Chen  ER diagram is widely used in database design  Represent conceptual level of a database system  Describe things and their relationships in high level  The diagram consists of a small set of symbols, there are more than one notation model most important are for Chen model symbols, and Crow’s Foot Model
(ER) model • The entity-relationship (ER) model – Basic constructs: • Entities • Relationships • Attributes (of entities and relationships) – Advanced constructs: • Constraints • Weak entities • Aggregation 7
ERD Elements • Entities – Things about which you collect information • Relationships – Means of association between entities • Identifiers – Unique attributes of the entity • Attributes – Characteristic or property of the entity that is of interest
9 9 Entity ►is a real-world object distinguishable or unique from other objects. ►An entity can be a concrete or physical object like employee, student, faculty, customer etc. Or it could also be conceptual or abstract like transaction, order, course, subjects etc. ►It can be thought of as a noun like student, employee etc. ►It is normally represented by a rectangle shape.
10 10 Relationship ►is a way of relating one entity to another. Entities can therefore participate in a relationship. ►it is commonly thought as a verb connecting the entities or nouns. ►It is normally represented by a diamond shape.
11 11 Example of Entities with Relationship Person belongs Location Student enrolls Subject(s) Faculty teaches Subject(s)
12 12 Types of Relationship ►One-to-One ►One-to-Many ►Many-to-Many
13 13 Types of Relationship Student has ID Division has Program Student enrolls Subject 1 1 1 M MM One-to-One One-to-Many Many-to-Many
14 14 Types of Relationship (Crow Notation) Student has ID Division has Program Student enrolls Subject One-to-One One-to-Many Many-to-Many
Mapping Cardinalities • One-to-One • One-to-Many • Many-to-One • Many-to-Many customer has account customer has account customer has account customer has account
Multicity Symbols M-to-N1-to-1 1-to M M-to-1
17 17 Attribute ►Refers to the characteristic or basic fact or field of an Entity or Relationship. ►For example a Student entity could have the following attributes ID Number, Last Name, First Name, Address, Birth Date etc. ►A relationship could also have an attribute for example an Entity name Student enrolls (relationship) to a Course/Program. Now, when you enroll you enroll on a certain date so you will have an attribute of Enrollment Date under Enroll relationship ►It is normally represented by a circle, but in some other notation may be different.
18 Entity Set to Relation Product name category price Product(name, category, price) name category price gizmo gadgets $19.99
19 19 Example of Attributes Student ID No. Lastname Firstname Gender Address Birth date Email Note : A Primary Key is Underlined, in this case the ID No.
20 20 Example of Attributes Student ID No. Lastname Firstname Gender Address Birth date Email enrollsProgram Enrollment Date Program ID Name Chairperson has Faculty ID No. Lastname Firstname
21 21 Example of Attributes Student ID No. Lastname Firstname Gender Address Birth date Email enrollsProgram Enrollment Date Program ID Name Chairperson has Faculty ID No. Lastname Firstname
Note that • Relationships: diamond (may or may not be used), on a line showing the “cardinality” of the relationship (1 to many), etc. • Identifiers: Underlined text • Attributes: It may be not shown
SUMMARY OF ER-DIAGRAM CHEN NOTATION/SYMBOLES Multicity Symbols
Weak Entity • Weak Entity set: An entity set that does not have enough attributes to form a primary key. • it must use a foreign key in conjunction with its attributes to create a primary key. The foreign key is typically a primary key of an entity it is related to.
Weak Entity
Composite, Multi Valued, and Derived Attributes Composite attributes: Composite attributes can be divided into subparts. For example, an attribute name could be structured as a composite attribute consisting of first-name, middle-initial, and last-name. Multivalued attributes: There may be instances where an attribute has a set of values for a specific entity. Consider an employee entity set with the attribute phone-number. An employee may have zero, one, or several phone numbers, and different employees may have different numbers of phones. Derived attribute: • The last category that attributes can be defined is called a derived attribute, where one attribute is calculated from another attribute. The derived attribute may not be stored in the database but rather calculated using algorithm.
Database part3-
Strong Entity Relation: ssno name salary employee Employee(ssno name salary) Key : ssno ER to Relational Mapping
Online ER diagram creator • https://erdplus.com/#/
VISIO- Program
Table: Employee Entity
Table: Employee Employee number Name Attributes
Table: Employee Employee number Name Birth Date Age Salary Key Attribute
Table: Employee Employee number Name Address Age Salary Composite Attribute
Table: Employee Employee number Name Address Age Salary Multi Valued Attribute
Table: Employee Employee number Name Address Age Salary Single Valued Attribute
Table: Employee Employee number Name Address Fax No / Tele. No Salary Null Valued Attribute
Table: Employee Employee number Name Birth Date Age Salary Derived
Employee Attributes Emp_no Birth Date Age Salary Name
Key Attribute Emp_no Employee Birth Date Salary Name
Employee Multi valued Attribute Emp_no Name Salary Name
Employee Name Street Address Area City Composite Attribute
Employee Emp_no Birth Date Age Salary Name Derived Attributes
RelationshipWorks Link
Manager Mno Name Salary Birth Date Department Mno Dname Works 11
Employee Empno Name Salary Birth Date Department Empno Dname Works 1M
Employee Empno Name Salary Project PId Ptype Works NM Start date End date
ER Diagram Of Banking System Bank Bank branch Branches Account Acct no Balance Acc Type Accts Loans Loan Loan no Amount Loan Type 1 M 1 M 1 M Bno Addr Name Code Addr
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Examples
Examples
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56 Step 1 Build Conceptual Data • To build a conceptual data model of the data requirements of the enterprise. – Model comprises entity types, relationship types, attributes and attribute domains, primary and alternate keys, and integrity constraints. • Step 1.1 Identify entity types – To identify the required entity types. • Step 1.2 Identify relationship types – To identify the important relationships that exist between the entity types.
57 Step 1 Build Conceptual Data • Step 1.3 Identify and associate attributes with entity or relationship types – To associate attributes with the appropriate entity or relationship types and document the details of each attribute. • Step 1.4 Determine attribute domains – To determine domains for the attributes in the data model and document the details of each domain.
58 Step 1 Build Conceptual Data • Step 1.5 Determine candidate, primary, and alternate key attributes – To identify the candidate key(s) for each entity and if there is more than one candidate key, to choose one to be the primary key and the others as alternate keys. • Step 1.6 Check model for redundancy – To check for the presence of any redundancy in the model and to remove any that does exist. • Step 1.7 Validate conceptual model against user transactions – To ensure that the conceptual model supports the required transactions.
Converting a text description into an E-R model: Review the conceptual description of the business area for nouns that describe the system, and to be an entity. Each entity type should have more than one attribute. Look for verbs to be the relation that connect the entities. Determine the expect multiplicity between entities.
Example: building ER diagram for a university A university consists of a number of departments. Each department offers several courses. A number of modules make up each course. Students enrol in a particular course and take modules towards the completion of that course. Each module is taught by a lecturer from the appropriate department, and each lecturer tutors a group of students 60
Example - Entities A university consists of a number of departments. Each department offers several courses. A number of modules make up each course. Students enrol in a particular course and take modules towards the completion of that course. Each module is taught by a lecturer from the appropriate department, and each lecturer tutors a group of students 61
Example - Relationships • A university consists of a number of departments. Each department offers several courses. • A number of modules make up each course. • Students enrol in a particular course and take modules towards the completion of that course. • Each module is taught by a lecturer from the appropriate department, and each lecturer tutors a group of students 62
Example - E/R Diagram ModuleCourse Department Student Lecturer Entities: Department, Course, Module, Lecturer, Student 63
Example - E/R Diagram ModuleCourse Department Student Lecturer Offers Each department offers several courses 64
Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers A number of modules make up each courses 65
Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers Enrols In Students enrol in a particular course 66
Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers Enrols In Takes Students … take modules 67
Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers Enrols In Takes Teaches Each module is taught by a lecturer 68
Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers Enrols In Takes Employs Teaches a lecturer from the appropriate department 69
Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers TutorsEnrols In Takes Employs Teaches each lecturer tutors a group of students 70
Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers TutorsEnrols In Takes Employs Teaches 71
Database part3-
desc desc
Converting ER diagrams into SQL
Class diagram • The Unified Modeling Language (UML) was designed for software engineering of large systems using object-oriented (OO) programming languages. • UML is a very large language; which can be implemented for different tasks. • http://www.tomjewett.com/dbdesign/dbdesign.php?p age=models.html
76 ER vs. UML Terminology (Class diagram) ER Diagram Entity Type Entity Attribute Domain ~ [Derived Attribute] Relationship Type Cardinality • UML Class Diagram • Class • Object • Attribute • Domain • Operation • Association • Multiplicities
Classes ClassName attributes operations A class is a description of a set of objects that share the same attributes, operations, relationships. Graphically, a class is rendered as a rectangle, usually including its name, attributes, and operations in separate, designated compartments. The operation includes any calculations such as average, account, sum ,max, etc
ER vs. Class diagram Employee E# FNAME LNAME NAME Employee NAME: FNAME LNAME … Attributes Methods or operation Class
Example for class diagram for a database
Example for class diagram for a database
Normalization Forms NF 81
82 Introduction Relational Designing Levels PersonbuysProduct name price name ssn Conceptual Model: Relational Model: Normalization: Eliminates anomalies (inconsistence) by decomposing tables, using Normalized forms
What is Normalization? 83 Normalization is the process of decomposing unsatisfactory "bad" relations by breaking up their attributes into smaller relations The objective of normalization: “to create relations where every dependency is on the key, the whole key, and nothing but the key”. Normalization = Standardization. In database means put the table in standard form.
84 Why the Normalization? • To produce well-structured relations – Any relational database should contain minimal data redundancy and allows users to insert, delete, and update rows without causing data inconsistencies (anomalies). – Data redundancy is a case within a database in which the same piece of data is held in two separate places.
• To make a normalized table you have to know about the meaning of each attribute, and how it can be uniquely connected to other one, and what is the compromise to minimize number of repeating values, in column and in rows or in both, and what are the candid keys. • It needs some practice to do it.
Anomalies and redundancy example What if the supplier GlassCo moves to new address Olympia? Or what if GlassCo become no more a supplier, how many fields needed to be deleted. Also, there are many repeated data of this GlassCo. Part# Description Supplier Address City State 100 Coil Dynar 45 Eastern Ave. Denver CO 101 Muffler GlassCo 1638 S. Front Seattle WA 102 Wheel Cover A1 Auto 7441 E. 4th Street Detroit MI 103 Battery Dynar 45 Estern Ave. Denver CO 104 Radiator United Parts 346 Taylor Drive Austin TX 105 Manifold GlassCo 1638 S. Front Seattle WA 106 Converter GlassCo 1638 S. Front Seattle WA 107 Tail Pipe GlassCo 1638 S. Front Seattle WA
A Typical Spreadsheet File (unnormalized) Emp No Employee Name Time Card No Time Card Date Dept No Dept Name 10 Thomas Arquette 106 11/02/2002 20 Marketing 10 Thomas Arquette 106 11/02/2002 20 Marketing 10 Thomas Arquette 106 11/02/2002 20 Marketing 10 Thomas Arquette 115 11/09/2002 20 Marketing 99 Janice Smitty 10 Accounting 500 Alan Cook 107 11/02/2002 50 Shipping 500 Alan Cook 107 11/02/2002 50 Shipping 700 Ernest Gold 108 11/02/2002 50 Shipping 700 Ernest Gold 116 11/09/2002 50 Shipping 700 Ernest Gold 116 11/09/2002 50 Shipping Unnormalized means There are multivalued attributes or repeating groups
Breaking the file into 3 tables eliminate the data redundancy (normalized tables) EmpNo EmpFirstName EmpLastName DeptNo 10 Thomas Arquette 20 500 Alan Cook 50 700 Ernest Gold 50 99 Janice Smitty 10 TimeCardNo EmpNo TimeCardDate 106 10 11/02/2002 107 500 11/02/2002 108 700 11/02/2002 115 10 11/09/2002 116 700 11/09/2002 Table: Employees Table: Time Card Data DeptNo DeptName 10 Accounting 20 Marketing 50 Shipping Table: Departments Primary Key
Database part3-
90 Another Normalization Example Name Credit Number City Fred 123-45-6789 Seattle Joe 987-65-4321 Westfield Credit Number PhoneNumber 123-45-6789 206-555-1234 123-45-6789 206-555-6543 987-65-4321 908-555-2121 Anomalies have gone: • No more repeated data • Easy to move Fred to “Bellevue” (how ?) • Easy to delete all Joe’s phone number (how ?) Name Credit Number PhoneNumber City Fred 123-45-6789 206-555-1234 Seattle Fred 123-45-6789 206-555-6543 Seattle Joe 987-65-4321 908-555-2121 Westfield
Why Normalized Tables? • Save typing of repetitive data • Increase flexibility to query, sort, summarize, and group data (Simpler to manipulate data!) • Avoid frequent restructuring of tables and other objects to accommodate new data • Reduce disk space
• How we can create normalized tables? • Apply the normalization forms • What are the normalization forms?
Types of normalization forms 93 The most important four normal forms are: 1NF is considered the weakest, 2NF is stronger than 1NF, 3NF is stronger than 2NF, and BCNF ( Boyce Codd) is considered the strongest Also, any relation that is in BCNF, is in 3NF; any relation in 3NF is in 2NF; and any relation in 2NF is in 1NF. For most business database design purposes, 3NF is as high as we need to go in normalization process.
Normal Forms: requirements • 1 NF – No multivalued attributes or repeating groups. • 2 NF – 1 NF + no partial dependencies • 3 NF – 2 NF + no transitive dependencies
Dependencies: Definitions • Partial Dependency – when an non-key attribute is determined by a part, but not the whole, of a COMPOSITE primary key. • Name depend on part of the composite key (cust ID), but it does not depend on the other part of the key (Order ID). CUSTOMER Cust_ID Name Order_ID 101 AT&T 1234 101 AT&T 156 125 Cisco 1250 Partial Dependency Dependency Diagram composite key composite key
FULLAND PARTIAL FUNCTIONAL DEPENDENCY • Grade is fully functionally dependent on the primary key (ID,Course- ID) because both parts of the primary keys are needed to determine Grade • On the other hand both Name and Phone attributes are partially dependent on the primary key, because only a part of the primary key namely ID is needed to determine them and similarly Credit-Hours and Course-Name can be determined using Course-ID .
Dependencies: Definitions • Transitive Dependency – when a non-key attribute determines another non-key attribute. EMPLOYEE Emp_ID F_Name L_Name Dept_ID Dept_Name 111 Mary Jones 1 Acct 122 Sarah Smith 2 Mktg Transitive Dependency Dependency Diagram
98 First Normal Form (1NF) • To be in First Normal Form (1NF), – Each table has a primary key: minimal set of attributes which can uniquely identify a record – The values in each column of a table are atomic (No multi-value attributes allowed). – There are no repeating groups: two columns do not store similar information in the same table.
Database part3-
1NF
Example: Tables Violating First Normal Form PART (Primary Key) WAREHOUSE P0010 Warehouse A, Warehouse B, Warehouse C P0020 Warehouse B, Warehouse D PART (Primary Key) WAREHOUSE A WAREHOUSE B WAREHOUSE C P0010 Yes No Yes P0020 No Yes Yes Really Bad Set-up! Better,
Example: Table in First Normal Form Fields contain smallest meaningful values EmpID FName LName Manager Dept Sector Spouse Child1 Child2 Child3 285 Carl Carlson Smithers Eng. 6G 365 Lenny Smithers Marketing 8G 458 Homer Simpson Mr. Burns Safety 7G Marge Bart Lisa Maggie EmpID Name Manager Dept Sector Spouse/Children 285 Carl Carlson Smithers Engineering 6G 365 Lenny Smithers Marketing 8G 458 Homer Simpson Mr. Burns Safety 7G Marge, Bart, Lisa, Maggie
Table in First Normal Form EmpID FName LName Manager Department Sector Dependent 285 Carl Carlson Smithers Engineering 6G 365 Lenny Smithers Marketing 8G 458 Homer Simpson Mr. Burns Safety 7G Marge 458 Homer Simpson Mr. Burns Safety 7G Bart 458 Homer Simpson Mr. Burns Safety 7G Lisa 458 Homer Simpson Mr. Burns Safety 7G Maggie EmpID Name Manager Dept Sector Spouse/Children 285 Carl Carlson Smithers Engineering 6G 365 Lenny Smithers Marketing 8G 458 Homer Simpson Mr. Burns Safety 7G Marge, Bart, Lisa, Maggie
Database part3-
105 Another 1NF Example Cust_ID L_Name F_Name Address 104 Suchecki Ray 123 Pond Hill Road, Detroit, 48161 Cust_ID SalesRep_Name Rep_Office Order_1 Order_2 Order_3 1022 Jones 412 10 14 19 Apply the 1NF to the following tables:
2NF and 3NF • 2NF and 3NF needs to understand the relation between the primary, composite, or candid keys to the other attributes,
2nd Normal Form • The requirements to satisfy the 2nd NF: • There is no redundancy of data (all data is stored in only one place). – Any non-key field should be dependent on the entire primary key. – The resulting tables must be related to each other by use of foreign key.
Age depended on part of the composite key Name, but not depend on the other key part Subject
Example Electric Toothbrush Models Manufacturer Model Model Full Name Manufacturer Country Forte X-Prime Forte X-Prime Italy Forte Ultraclean Forte Ultraclean Italy Dent-o-Fresh EZbrush Dent-o-Fresh EZbrush USA Kobayashi ST-60 Kobayashi ST-60 Japan Hoch Toothmaster Hoch Toothmaster Germany Hoch X-Prime Hoch X-Prime Germany To make this table follow 2NF, it is necessary to have two relations: There is no primary key can be determined where the other nonkey depend on it in the below table.
Manufacturer Manufacturer Country Forte Italy Dent-o-Fresh USA Kobayashi Japan Hoch Germany Electric Toothbrush Manufacturers Manufacturer Model Model Full Name Forte X-Prime Forte X-Prime Forte Ultraclean Forte Ultraclean Dent-o-Fresh EZbrush Dent-o-Fresh EZbrush Kobayashi ST-60 Kobayashi ST-60 Hoch Toothmaster Hoch Toothmaster Hoch X-Prime Hoch X-Prime Electric Toothbrush Models
Database part3-
112 Third Normal Form • In order to be in Third Normal Form, a relation must first fulfill the requirements to be in 2NF. • Additionally, all attributes that are not dependent upon the primary key must be eliminated. In other words, there should be no transitive dependencies: (No non-key fields are dependent on another non-key field) • Solution: non-key determinant with transitive dependencies go into a new table; non-key determinant becomes primary key in the new table and stays as foreign key in the old table
Example: Bringing a Relation to 3NF EMPLOYEE Emp_ID F_Name L_Name Dept_ID 111 Mary Jones 1 122 Sarah Smith 2 EMPLOYEE Emp_ID F_Name L_Name Dept_ID Dept_Name 111 Mary Jones 1 Acct 122 Sarah Smith 2 Mktg DEPARTMENT Dept_ID Dept_Name 1 Acct 2 Mktg Non key Dept Name dependt on Dept ID which is non key field in the first table.
Example 1: 1NF, 2NF, and 3N
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End of part 3 end of the Course 120

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Database part3-

  • 1. Course code: ITI131 Course title : Database PART: 3 Prof. Taymoor Mohamed Nazmy Dept. of computer science, faculty of computer science, Ain Shams uni. Ex-vice dean of post graduate studies and research Cairo, Egypt 1
  • 2. Database design & E/R model 2
  • 5. Steps in Database Design • Requirements Analysis – user needs; what must database do? • Conceptual Design – high level description (often done w/ER model) • Logical Design – translate ER into DBMS data model • Schema Refinement – consistency, normalization • Physical Design - indexes, disk layout • Security Design - who accesses what, and how 5
  • 6. 6 Entity Relation (ER) Diagram  1976 proposed by Peter Chen  ER diagram is widely used in database design  Represent conceptual level of a database system  Describe things and their relationships in high level  The diagram consists of a small set of symbols, there are more than one notation model most important are for Chen model symbols, and Crow’s Foot Model
  • 7. (ER) model • The entity-relationship (ER) model – Basic constructs: • Entities • Relationships • Attributes (of entities and relationships) – Advanced constructs: • Constraints • Weak entities • Aggregation 7
  • 8. ERD Elements • Entities – Things about which you collect information • Relationships – Means of association between entities • Identifiers – Unique attributes of the entity • Attributes – Characteristic or property of the entity that is of interest
  • 9. 9 9 Entity ►is a real-world object distinguishable or unique from other objects. ►An entity can be a concrete or physical object like employee, student, faculty, customer etc. Or it could also be conceptual or abstract like transaction, order, course, subjects etc. ►It can be thought of as a noun like student, employee etc. ►It is normally represented by a rectangle shape.
  • 10. 10 10 Relationship ►is a way of relating one entity to another. Entities can therefore participate in a relationship. ►it is commonly thought as a verb connecting the entities or nouns. ►It is normally represented by a diamond shape.
  • 11. 11 11 Example of Entities with Relationship Person belongs Location Student enrolls Subject(s) Faculty teaches Subject(s)
  • 13. 13 13 Types of Relationship Student has ID Division has Program Student enrolls Subject 1 1 1 M MM One-to-One One-to-Many Many-to-Many
  • 14. 14 14 Types of Relationship (Crow Notation) Student has ID Division has Program Student enrolls Subject One-to-One One-to-Many Many-to-Many
  • 15. Mapping Cardinalities • One-to-One • One-to-Many • Many-to-One • Many-to-Many customer has account customer has account customer has account customer has account
  • 17. 17 17 Attribute ►Refers to the characteristic or basic fact or field of an Entity or Relationship. ►For example a Student entity could have the following attributes ID Number, Last Name, First Name, Address, Birth Date etc. ►A relationship could also have an attribute for example an Entity name Student enrolls (relationship) to a Course/Program. Now, when you enroll you enroll on a certain date so you will have an attribute of Enrollment Date under Enroll relationship ►It is normally represented by a circle, but in some other notation may be different.
  • 18. 18 Entity Set to Relation Product name category price Product(name, category, price) name category price gizmo gadgets $19.99
  • 19. 19 19 Example of Attributes Student ID No. Lastname Firstname Gender Address Birth date Email Note : A Primary Key is Underlined, in this case the ID No.
  • 20. 20 20 Example of Attributes Student ID No. Lastname Firstname Gender Address Birth date Email enrollsProgram Enrollment Date Program ID Name Chairperson has Faculty ID No. Lastname Firstname
  • 21. 21 21 Example of Attributes Student ID No. Lastname Firstname Gender Address Birth date Email enrollsProgram Enrollment Date Program ID Name Chairperson has Faculty ID No. Lastname Firstname
  • 22. Note that • Relationships: diamond (may or may not be used), on a line showing the “cardinality” of the relationship (1 to many), etc. • Identifiers: Underlined text • Attributes: It may be not shown
  • 23. SUMMARY OF ER-DIAGRAM CHEN NOTATION/SYMBOLES Multicity Symbols
  • 24. Weak Entity • Weak Entity set: An entity set that does not have enough attributes to form a primary key. • it must use a foreign key in conjunction with its attributes to create a primary key. The foreign key is typically a primary key of an entity it is related to.
  • 26. Composite, Multi Valued, and Derived Attributes Composite attributes: Composite attributes can be divided into subparts. For example, an attribute name could be structured as a composite attribute consisting of first-name, middle-initial, and last-name. Multivalued attributes: There may be instances where an attribute has a set of values for a specific entity. Consider an employee entity set with the attribute phone-number. An employee may have zero, one, or several phone numbers, and different employees may have different numbers of phones. Derived attribute: • The last category that attributes can be defined is called a derived attribute, where one attribute is calculated from another attribute. The derived attribute may not be stored in the database but rather calculated using algorithm.
  • 28. Strong Entity Relation: ssno name salary employee Employee(ssno name salary) Key : ssno ER to Relational Mapping
  • 29. Online ER diagram creator • https://erdplus.com/#/
  • 33. Table: Employee Employee number Name Birth Date Age Salary Key Attribute
  • 34. Table: Employee Employee number Name Address Age Salary Composite Attribute
  • 35. Table: Employee Employee number Name Address Age Salary Multi Valued Attribute
  • 36. Table: Employee Employee number Name Address Age Salary Single Valued Attribute
  • 37. Table: Employee Employee number Name Address Fax No / Tele. No Salary Null Valued Attribute
  • 48. ER Diagram Of Banking System Bank Bank branch Branches Account Acct no Balance Acc Type Accts Loans Loan Loan no Amount Loan Type 1 M 1 M 1 M Bno Addr Name Code Addr
  • 56. 56 Step 1 Build Conceptual Data • To build a conceptual data model of the data requirements of the enterprise. – Model comprises entity types, relationship types, attributes and attribute domains, primary and alternate keys, and integrity constraints. • Step 1.1 Identify entity types – To identify the required entity types. • Step 1.2 Identify relationship types – To identify the important relationships that exist between the entity types.
  • 57. 57 Step 1 Build Conceptual Data • Step 1.3 Identify and associate attributes with entity or relationship types – To associate attributes with the appropriate entity or relationship types and document the details of each attribute. • Step 1.4 Determine attribute domains – To determine domains for the attributes in the data model and document the details of each domain.
  • 58. 58 Step 1 Build Conceptual Data • Step 1.5 Determine candidate, primary, and alternate key attributes – To identify the candidate key(s) for each entity and if there is more than one candidate key, to choose one to be the primary key and the others as alternate keys. • Step 1.6 Check model for redundancy – To check for the presence of any redundancy in the model and to remove any that does exist. • Step 1.7 Validate conceptual model against user transactions – To ensure that the conceptual model supports the required transactions.
  • 59. Converting a text description into an E-R model: Review the conceptual description of the business area for nouns that describe the system, and to be an entity. Each entity type should have more than one attribute. Look for verbs to be the relation that connect the entities. Determine the expect multiplicity between entities.
  • 60. Example: building ER diagram for a university A university consists of a number of departments. Each department offers several courses. A number of modules make up each course. Students enrol in a particular course and take modules towards the completion of that course. Each module is taught by a lecturer from the appropriate department, and each lecturer tutors a group of students 60
  • 61. Example - Entities A university consists of a number of departments. Each department offers several courses. A number of modules make up each course. Students enrol in a particular course and take modules towards the completion of that course. Each module is taught by a lecturer from the appropriate department, and each lecturer tutors a group of students 61
  • 62. Example - Relationships • A university consists of a number of departments. Each department offers several courses. • A number of modules make up each course. • Students enrol in a particular course and take modules towards the completion of that course. • Each module is taught by a lecturer from the appropriate department, and each lecturer tutors a group of students 62
  • 63. Example - E/R Diagram ModuleCourse Department Student Lecturer Entities: Department, Course, Module, Lecturer, Student 63
  • 64. Example - E/R Diagram ModuleCourse Department Student Lecturer Offers Each department offers several courses 64
  • 65. Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers A number of modules make up each courses 65
  • 66. Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers Enrols In Students enrol in a particular course 66
  • 67. Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers Enrols In Takes Students … take modules 67
  • 68. Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers Enrols In Takes Teaches Each module is taught by a lecturer 68
  • 69. Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers Enrols In Takes Employs Teaches a lecturer from the appropriate department 69
  • 70. Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers TutorsEnrols In Takes Employs Teaches each lecturer tutors a group of students 70
  • 71. Example - E/R Diagram ModuleCourse Department Student LecturerIncludes Offers TutorsEnrols In Takes Employs Teaches 71
  • 75. Class diagram • The Unified Modeling Language (UML) was designed for software engineering of large systems using object-oriented (OO) programming languages. • UML is a very large language; which can be implemented for different tasks. • http://www.tomjewett.com/dbdesign/dbdesign.php?p age=models.html
  • 76. 76 ER vs. UML Terminology (Class diagram) ER Diagram Entity Type Entity Attribute Domain ~ [Derived Attribute] Relationship Type Cardinality • UML Class Diagram • Class • Object • Attribute • Domain • Operation • Association • Multiplicities
  • 77. Classes ClassName attributes operations A class is a description of a set of objects that share the same attributes, operations, relationships. Graphically, a class is rendered as a rectangle, usually including its name, attributes, and operations in separate, designated compartments. The operation includes any calculations such as average, account, sum ,max, etc
  • 78. ER vs. Class diagram Employee E# FNAME LNAME NAME Employee NAME: FNAME LNAME … Attributes Methods or operation Class
  • 79. Example for class diagram for a database
  • 80. Example for class diagram for a database
  • 82. 82 Introduction Relational Designing Levels PersonbuysProduct name price name ssn Conceptual Model: Relational Model: Normalization: Eliminates anomalies (inconsistence) by decomposing tables, using Normalized forms
  • 83. What is Normalization? 83 Normalization is the process of decomposing unsatisfactory "bad" relations by breaking up their attributes into smaller relations The objective of normalization: “to create relations where every dependency is on the key, the whole key, and nothing but the key”. Normalization = Standardization. In database means put the table in standard form.
  • 84. 84 Why the Normalization? • To produce well-structured relations – Any relational database should contain minimal data redundancy and allows users to insert, delete, and update rows without causing data inconsistencies (anomalies). – Data redundancy is a case within a database in which the same piece of data is held in two separate places.
  • 85. • To make a normalized table you have to know about the meaning of each attribute, and how it can be uniquely connected to other one, and what is the compromise to minimize number of repeating values, in column and in rows or in both, and what are the candid keys. • It needs some practice to do it.
  • 86. Anomalies and redundancy example What if the supplier GlassCo moves to new address Olympia? Or what if GlassCo become no more a supplier, how many fields needed to be deleted. Also, there are many repeated data of this GlassCo. Part# Description Supplier Address City State 100 Coil Dynar 45 Eastern Ave. Denver CO 101 Muffler GlassCo 1638 S. Front Seattle WA 102 Wheel Cover A1 Auto 7441 E. 4th Street Detroit MI 103 Battery Dynar 45 Estern Ave. Denver CO 104 Radiator United Parts 346 Taylor Drive Austin TX 105 Manifold GlassCo 1638 S. Front Seattle WA 106 Converter GlassCo 1638 S. Front Seattle WA 107 Tail Pipe GlassCo 1638 S. Front Seattle WA
  • 87. A Typical Spreadsheet File (unnormalized) Emp No Employee Name Time Card No Time Card Date Dept No Dept Name 10 Thomas Arquette 106 11/02/2002 20 Marketing 10 Thomas Arquette 106 11/02/2002 20 Marketing 10 Thomas Arquette 106 11/02/2002 20 Marketing 10 Thomas Arquette 115 11/09/2002 20 Marketing 99 Janice Smitty 10 Accounting 500 Alan Cook 107 11/02/2002 50 Shipping 500 Alan Cook 107 11/02/2002 50 Shipping 700 Ernest Gold 108 11/02/2002 50 Shipping 700 Ernest Gold 116 11/09/2002 50 Shipping 700 Ernest Gold 116 11/09/2002 50 Shipping Unnormalized means There are multivalued attributes or repeating groups
  • 88. Breaking the file into 3 tables eliminate the data redundancy (normalized tables) EmpNo EmpFirstName EmpLastName DeptNo 10 Thomas Arquette 20 500 Alan Cook 50 700 Ernest Gold 50 99 Janice Smitty 10 TimeCardNo EmpNo TimeCardDate 106 10 11/02/2002 107 500 11/02/2002 108 700 11/02/2002 115 10 11/09/2002 116 700 11/09/2002 Table: Employees Table: Time Card Data DeptNo DeptName 10 Accounting 20 Marketing 50 Shipping Table: Departments Primary Key
  • 90. 90 Another Normalization Example Name Credit Number City Fred 123-45-6789 Seattle Joe 987-65-4321 Westfield Credit Number PhoneNumber 123-45-6789 206-555-1234 123-45-6789 206-555-6543 987-65-4321 908-555-2121 Anomalies have gone: • No more repeated data • Easy to move Fred to “Bellevue” (how ?) • Easy to delete all Joe’s phone number (how ?) Name Credit Number PhoneNumber City Fred 123-45-6789 206-555-1234 Seattle Fred 123-45-6789 206-555-6543 Seattle Joe 987-65-4321 908-555-2121 Westfield
  • 91. Why Normalized Tables? • Save typing of repetitive data • Increase flexibility to query, sort, summarize, and group data (Simpler to manipulate data!) • Avoid frequent restructuring of tables and other objects to accommodate new data • Reduce disk space
  • 92. • How we can create normalized tables? • Apply the normalization forms • What are the normalization forms?
  • 93. Types of normalization forms 93 The most important four normal forms are: 1NF is considered the weakest, 2NF is stronger than 1NF, 3NF is stronger than 2NF, and BCNF ( Boyce Codd) is considered the strongest Also, any relation that is in BCNF, is in 3NF; any relation in 3NF is in 2NF; and any relation in 2NF is in 1NF. For most business database design purposes, 3NF is as high as we need to go in normalization process.
  • 94. Normal Forms: requirements • 1 NF – No multivalued attributes or repeating groups. • 2 NF – 1 NF + no partial dependencies • 3 NF – 2 NF + no transitive dependencies
  • 95. Dependencies: Definitions • Partial Dependency – when an non-key attribute is determined by a part, but not the whole, of a COMPOSITE primary key. • Name depend on part of the composite key (cust ID), but it does not depend on the other part of the key (Order ID). CUSTOMER Cust_ID Name Order_ID 101 AT&T 1234 101 AT&T 156 125 Cisco 1250 Partial Dependency Dependency Diagram composite key composite key
  • 96. FULLAND PARTIAL FUNCTIONAL DEPENDENCY • Grade is fully functionally dependent on the primary key (ID,Course- ID) because both parts of the primary keys are needed to determine Grade • On the other hand both Name and Phone attributes are partially dependent on the primary key, because only a part of the primary key namely ID is needed to determine them and similarly Credit-Hours and Course-Name can be determined using Course-ID .
  • 97. Dependencies: Definitions • Transitive Dependency – when a non-key attribute determines another non-key attribute. EMPLOYEE Emp_ID F_Name L_Name Dept_ID Dept_Name 111 Mary Jones 1 Acct 122 Sarah Smith 2 Mktg Transitive Dependency Dependency Diagram
  • 98. 98 First Normal Form (1NF) • To be in First Normal Form (1NF), – Each table has a primary key: minimal set of attributes which can uniquely identify a record – The values in each column of a table are atomic (No multi-value attributes allowed). – There are no repeating groups: two columns do not store similar information in the same table.
  • 100. 1NF
  • 101. Example: Tables Violating First Normal Form PART (Primary Key) WAREHOUSE P0010 Warehouse A, Warehouse B, Warehouse C P0020 Warehouse B, Warehouse D PART (Primary Key) WAREHOUSE A WAREHOUSE B WAREHOUSE C P0010 Yes No Yes P0020 No Yes Yes Really Bad Set-up! Better,
  • 102. Example: Table in First Normal Form Fields contain smallest meaningful values EmpID FName LName Manager Dept Sector Spouse Child1 Child2 Child3 285 Carl Carlson Smithers Eng. 6G 365 Lenny Smithers Marketing 8G 458 Homer Simpson Mr. Burns Safety 7G Marge Bart Lisa Maggie EmpID Name Manager Dept Sector Spouse/Children 285 Carl Carlson Smithers Engineering 6G 365 Lenny Smithers Marketing 8G 458 Homer Simpson Mr. Burns Safety 7G Marge, Bart, Lisa, Maggie
  • 103. Table in First Normal Form EmpID FName LName Manager Department Sector Dependent 285 Carl Carlson Smithers Engineering 6G 365 Lenny Smithers Marketing 8G 458 Homer Simpson Mr. Burns Safety 7G Marge 458 Homer Simpson Mr. Burns Safety 7G Bart 458 Homer Simpson Mr. Burns Safety 7G Lisa 458 Homer Simpson Mr. Burns Safety 7G Maggie EmpID Name Manager Dept Sector Spouse/Children 285 Carl Carlson Smithers Engineering 6G 365 Lenny Smithers Marketing 8G 458 Homer Simpson Mr. Burns Safety 7G Marge, Bart, Lisa, Maggie
  • 105. 105 Another 1NF Example Cust_ID L_Name F_Name Address 104 Suchecki Ray 123 Pond Hill Road, Detroit, 48161 Cust_ID SalesRep_Name Rep_Office Order_1 Order_2 Order_3 1022 Jones 412 10 14 19 Apply the 1NF to the following tables:
  • 106. 2NF and 3NF • 2NF and 3NF needs to understand the relation between the primary, composite, or candid keys to the other attributes,
  • 107. 2nd Normal Form • The requirements to satisfy the 2nd NF: • There is no redundancy of data (all data is stored in only one place). – Any non-key field should be dependent on the entire primary key. – The resulting tables must be related to each other by use of foreign key.
  • 108. Age depended on part of the composite key Name, but not depend on the other key part Subject
  • 109. Example Electric Toothbrush Models Manufacturer Model Model Full Name Manufacturer Country Forte X-Prime Forte X-Prime Italy Forte Ultraclean Forte Ultraclean Italy Dent-o-Fresh EZbrush Dent-o-Fresh EZbrush USA Kobayashi ST-60 Kobayashi ST-60 Japan Hoch Toothmaster Hoch Toothmaster Germany Hoch X-Prime Hoch X-Prime Germany To make this table follow 2NF, it is necessary to have two relations: There is no primary key can be determined where the other nonkey depend on it in the below table.
  • 110. Manufacturer Manufacturer Country Forte Italy Dent-o-Fresh USA Kobayashi Japan Hoch Germany Electric Toothbrush Manufacturers Manufacturer Model Model Full Name Forte X-Prime Forte X-Prime Forte Ultraclean Forte Ultraclean Dent-o-Fresh EZbrush Dent-o-Fresh EZbrush Kobayashi ST-60 Kobayashi ST-60 Hoch Toothmaster Hoch Toothmaster Hoch X-Prime Hoch X-Prime Electric Toothbrush Models
  • 112. 112 Third Normal Form • In order to be in Third Normal Form, a relation must first fulfill the requirements to be in 2NF. • Additionally, all attributes that are not dependent upon the primary key must be eliminated. In other words, there should be no transitive dependencies: (No non-key fields are dependent on another non-key field) • Solution: non-key determinant with transitive dependencies go into a new table; non-key determinant becomes primary key in the new table and stays as foreign key in the old table
  • 113. Example: Bringing a Relation to 3NF EMPLOYEE Emp_ID F_Name L_Name Dept_ID 111 Mary Jones 1 122 Sarah Smith 2 EMPLOYEE Emp_ID F_Name L_Name Dept_ID Dept_Name 111 Mary Jones 1 Acct 122 Sarah Smith 2 Mktg DEPARTMENT Dept_ID Dept_Name 1 Acct 2 Mktg Non key Dept Name dependt on Dept ID which is non key field in the first table.
  • 114. Example 1: 1NF, 2NF, and 3N
  • 120. End of part 3 end of the Course 120