1. Sahar Mosleh California State University San MarcosPage 1 Database Design and Administration By: Sahar Mosleh

2. California State University San MarcosPage 2 Relational Data Model

3. Sahar Mosleh California State University San MarcosPage 3 File Management Systems Before the existence of DBMS, the data were stored in separate files. There was no link from one file to another If the structure of the data changed (ex: adding more fields), programs that were using the file had to change Problems became more severe when the number of the programs using the files increased over time

4. Sahar Mosleh California State University San MarcosPage 4 Relational Data Model Definition: A relational database is a database where all data visible to users is organized strictly as tables of data values and where all database operations work on these tables In this model information is stored in a database as simple row/column tables of data Next slide shows an example of tables in a relational database

5. Sahar Mosleh California State University San MarcosPage 5 Empl_Num Name Age Rep_Office Title Hire_Date Manager Quota Sales 105 Bill Adams 37 13 Sales Rep 12-FEB-88 104 350000 367911 109 Mary Jones 31 11 Sales Rep 12-OCT-89 106 300000 392725 102 Sue Smith 48 21 Sales Rep 10-DEC-86 108 350000 474050 106 Sam Clark 52 11 VP Sales 14-JUN-88 275000 299912 104 Bob Smith 33 12 Sales Mgr 19-MAY-87 106 200000 142594 101 Dan Roberts 45 12 Sales Rep 20-OCT-86 104 300000 305673 110 Tom Synder 41 Sales Rep 13-JAN-90 101 75985 108 Larry Fitch 62 21 Sales Mgr 12-OCT-89 106 350000 361865 103 Paul Cruz 29 12 Sales Rep 01-MAR-87 104 275000 286775 1Nacy Angelli 49 22 Sales Rep 14-NOV-88 108 300000 186042 …. SalesReps Order_Num Order_Date Cust Rep MFR Product QTY Amount 112961 17-DEC-89 2117 106 REI 2A44L 7 31500 113012 11-JAN-90 2111 105 ACI 41003 35 3745 112989 03-JAN-90 2101 106 FEA 114 6 1458 113051 10-FEB-90 2118 108 QSA K47 4 1420 112968 12-OCT-89 2102 101 ACI 41004 34 3978 113036 30-JAN-90 2107 110 ACI 4100Z 9 22500 113045 02-FEB-90 2112 108 REI 2A44R 10 45000 112963 17-DEC-89 2103 105 ACI 41004 28 3276 113013 14-JAN-90 2118 108 BIC 41003 1 652 113058 23-FEB-90 2108 109 FEA 112 10 1480 112997 08-JAN-90 2124 107 BIC 41003 1 652 112983 27-DEC-89 2103 105 ACI 41004 6 702 113024 20-JAN-90 2114 108 QSA XK47 20 7100 113062 24-FEB-90 2124 107 FEA 114 10 2430 112979 12-OCT-89 2114 102 ACI 4100Z 6 15000 …… Orders Mfr_Id Product_Id Description Price Qty_On_Hand REI 2A45C RATCHET LINK 79 210 ACI 4100Y WIDGET REMOVER 2750 25 QSA XK47 REDUCER 355 38 BIC 41672 PLATE 180 0 IMM 779C 900-LB BRACE 1875 9 ACI 41003 SIZE 3 WIDGET 107 207 ACI 41004 SIZE 4 WIDGET 117 139 BIC 41003 HANDLE 652 3 IMM 887P BRACE PIN 250 24 QSA XK48 REDUCER 134 203 REI 2A44L LEFT HINGE 4500 12 …. Products Cust_Num Company Cust_Rep Credit_Limit 2111 JCP Inc. 103 50000 2102 First Corp. 101 65000 2103 Acme Mfg. 105 50000 2123 Carter and Sons 102 40000 2107 Ace International 110 35000 2115 Smithson Corp. 101 20000 2101 Jones Mfg. 106 65000 2112 Zetacorp 108 50000 2121 QMA Assoc. 103 45000 2114 Orion Corp. 102 20000 …… Customers Offices Office City Region Mgr Target Sales 22 Denver Western 108 300000 186042 11 New York Eastern 106 575000 692637 12 Chicago Eastern 104 800000 735042 13 Atlanta Eastern 105 350000 367911 21 Los Angeles Western 108 725000 835915

6. Sahar Mosleh California State University San MarcosPage 6 Table Definition: A table is a rectangular object with rows and columns For example in the office table: Each row of the office table represents a single physical entity Each column of the offices table represents one item of data that is stored in the database for each office: Ex: City column represents the location of the office An alternative term for column is attribute Each row of the table contains exactly one data value in each column

7. Sahar Mosleh California State University San MarcosPage 7 In each column of a table, all of the data values in that column have the same type. For example: City column values are words Sales values are money type Mgr values are integer Each column in a table has a column name which is written as a heading at the top of the column Column names must be unique in a table The columns of a table have a left-right order. That is defined when the table is first created. The order of the column has no effect when any action is done against the table

8. Sahar Mosleh California State University San MarcosPage 8 Each table must have at least one column Almost all commercial DBMS products impose maximum of 255 columns per table A table can have zero or more rows A table with zero rows is called an empty table Order of the rows is not important in a table. Most relational DBMSs either do not impose any limit on the number of rows or their limit is a very large number A common limit is approximately 2 billion rows

9. Sahar Mosleh California State University San MarcosPage 9 Primary Key Definition: A primary key is a column or combination of two or more columns that uniquely identifies each row of a table. Since the order of rows in a table is irrelevant, rows cannot be identified based on their positions in a table Ex: row 1, row 2, row 20 In a well-designed relational database each table has a primary key. If the primary key contains two or more columns, it is called a composite primary key

10. Sahar Mosleh California State University San MarcosPage 10 Example of primary key Consider the Offices table “Office” column (attribute) can be a good choice for the primary key because each office has a different office id However, city is not a good choice because more than one office may be located in the same city. Office City Region Mgr Target Sales 22 Denver Western 108 300000 186042 11 New York Eastern 106 575000 692637 12 Chicago Eastern 104 800000 735042 13 Atlanta Eastern 105 350000 367911 21 Los Angeles Western 108 725000 835915

11. Sahar Mosleh California State University San MarcosPage 11 Consider the Products table Mfr_Id Product_Id Description Price Qty_On_Hand REI 2A45C RATCHET LINK 79 210 ACI 4100Y WIDGET REMOVER 27.50 25 QSA XK47 REDUCER 355 38 BIC 41672 PLATE 180 0 IMM 779C 900-LB BRACE 1875 9 ACI 41003 SIZE 3 WIDGET 107 207 ACI 41004 SIZE 4 WIDGET 117 139 BIC 41003 HANDLE 652 3 IMM 887P BRACE PIN 250 24 QSA XK48 REDUCER 134 203 REI 2A44L LEFT HINGE 4500 12 …. What is a good primary key for this table?

12. Sahar Mosleh California State University San MarcosPage 12 In this case, MrfId by itself, is not a good choice to be a primary key because more than one manufacturer may produce more than one product Further, ProductId by itself is not a good choice either because the same product can be produced by more than one manufacturer. However, combination of both is unique in every row. This is an example of composite primary key. A table with a primary key is called a relation. A relation is a table in which no duplicate rows can exist.

13. Sahar Mosleh California State University San MarcosPage 13 Relationship How does the parent/child model is represented in the relational data model? Consider the following two tables Empl_Num Name Age Rep_Office Title Hire_Date Manager Quota Sales 105 Bill Adams 37 13 Sales Rep 12-FEB-88 104 350000 367911 109 Mary Jones 31 11 Sales Rep 12-OCT-89 106 300000 392725 102 Sue Smith 48 21 Sales Rep 10-DEC-86 108 350000 474050 106 Sam Clark 52 11 VP Sales 14-JUN-88 275000 299912 …. SalesReps Offices Office City Regin Mgr Target Sales 22 Denver Western 108 300000 186042 11 New York Eastern 106 575000 692637 12 Chicago Eastern 104 800000 735042 13 Atlanta Eastern 105 350000 367911 21 Los Angeles Western 108 725000 835915

14. Sahar Mosleh California State University San MarcosPage 14 The parent is the offices table The child is the salesreps table because the salesreps works in an office Relationships are created by having the same data in two or more tables Empl_Num Name Age Rep_Office Title Hire_Date Manager Quota Sales 105 Bill Adams 37 13 Sales Rep 12-FEB-88 104 350000 367911 109 Mary Jones 31 11 Sales Rep 12-OCT-89 106 300000 392725 102 Sue Smith 48 21 Sales Rep 10-DEC-86 108 350000 474050 106 Sam Clark 52 11 VP Sales 14-JUN-88 275000 299912 …. SalesReps Offices Office City Regin Mgr Target Sales 22 Denver Western 108 300000 186042 11 New York Eastern 106 575000 692637 12 Chicago Eastern 104 800000 735042 13 Atlanta Eastern 105 350000 367911 21 Los Angeles Western 108 725000 835915

15. Sahar Mosleh California State University San MarcosPage 15 Note that the RepOffice column in salesreps table contains the office number of the sales office where each sales person works The values of the RepOffice column is the set of office numbers found in the office column of the offices table We will see how this restriction is imposed when we discuss about creating tables later in the course For example, it is possible to find the sales office where “Mary Jones” is working by finding the value of Mary Jones RepOffice (11) and finding the corresponding row offices table So, the parent/child relationship between two tables A and B is not represented by explicit pointers but by common data values stored in the two tables Programmers must specify this relationship when they create the tables

16. Sahar Mosleh California State University San MarcosPage 16 Foreign Key Definition: Foreign key is a column (or combination or two or more columns) whose value matches the primary key of another table or possibly the same table Together, primary key and the foreign key make the parent/child relationship in relational data models Emp_Num Name Age Rep_Office Title Hire_Date Manager Quota Sales 105 Bill Adams 37 13 Sales Rep 12-FEB-88 104 350000 367911 109 Mary Jones 31 11 Sales Rep 12-OCT-89 106 300000 392725 102 Sue Smith 48 21 Sales Rep 10-DEC-86 108 350000 474050 106 Sam Clark 52 11 VP Sales 14-JUN-88 275000 299912 …. SalesReps Offices Office City Regin Mgr Target Sales 22 Denver Western 108 300000 186042 11 New York Eastern 106 575000 692637 12 Chicago Eastern 104 800000 735042 13 Atlanta Eastern 105 350000 367911 21 Los Angeles Western 108 725000 835915 Primary key Foreign key

17. Sahar Mosleh California State University San MarcosPage 17 Example of Foreign Key Empl_Num Name 105 Bill Adams 109 Mary Jones 102 Sue Smith 106 Sam Clark …. SalesReps Order_Num Order_Date Cust Rep Mfr Product QTY Amount 1129617-DEC-89 2117 106 REI 2A44L 7 31500 113012 11-JAN-90 2111 105 ACI 41003 35 3745 112989 03-JAN-90 2101 106 FEA 114 6 1458 113051 10-FEB-90 2118 108 QSA K47 4 1420 …. Orders Mfr_Id Product_Id REI 2A45C ….. ACI 4100Y ….. QSA XK47 …… …. ….. Products Cust_Num 2111 ….. 2102 …. 2103 …. ………. ……. Customers

18. Sahar Mosleh California State University San MarcosPage 18 Entity Relational Diagram (ERD) Modeling

19. Sahar Mosleh California State University San MarcosPage 19 ERD Model Entity-Relationship, ER Model ER model describes data as entities, relationships and attributes Entity A “thing” in the real world with an independent existence Physical existence Person, car, house or employee Conceptual existence Company, job, university course Attribute Property that describes entity employeeName, Address, Age, HomePhone companyName, Headquarters, President

20. Sahar Mosleh California State University San MarcosPage 20 Value A particular entity will have a value for each of its attributes The attribute values that describe each entity become a major part of the stored data Example employee: Name, Address, Age, HomePhone e1: “Bill Adams”, “561 Machray Hall”, “25”, “8831” e2: “John Smith”, “563 Queen Hall”, “30”, “8833”

21. Sahar Mosleh California State University San MarcosPage 21 Simple and Derived Attributes Simple attribute Attributes that are not divisible Ex: age, SSN, StudentId, etc Derived Attributes that can be derived from other attributes either from the same entity or other entities. For example: Age can be derived from BirthDate or GPA can be derived from Grades Attribute values can be derived from other entities. NumberOfEmployees of a department in department entity can be derived by counting the number of employees who work in that department in the employee entity

22. Sahar Mosleh California State University San MarcosPage 22 Null Values Not Applicable A particular entity does not have an applicable value for an attribute ApartmentNumber is null because the family lives in the house and not in an apartment CollegeDegrees is null because the person never gone to the college Unknown Missing (value exists but not known) Height of a person Not Known (existence is not sure) HomePhone, OfficePhone

23. Sahar Mosleh California State University San MarcosPage 23 Entity An entity defines a collection object that have the same attributes Entity is described by its name and attributes Example: Employee[Number, Name, Title, Salary] Project[Number, Budget, Location] Entity instances are instantiations of the entity Example: EmployeeJoe, Jim,... ProjectCompiler design, Accounting,...

24. Sahar Mosleh California State University San MarcosPage 24 ER Notation Entity Rectangular box Enclosing the entity name Attribute Name Oval Attached to its entity by straight line Composite Attribute Attached to the component attribute by straight line EMPLOYEE EmpId

25. Sahar Mosleh California State University San MarcosPage 25 Attribute Notations Regular Attribute Key Attribute Derived Attribute

26. Sahar Mosleh California State University San MarcosPage 26 Key Attribute Values can be used to identify each entity uniquely. This plays the role of primary key in a table The key attribute is underlined in ER diagram Composite key Attributes Combination of the two or more attributes must be distinct for each instance. This plays the role of composite primary key in a table Entities may have more than one attribute that can be chosen as key attribute. For example, StudentId and SSN. However, you only have to pick one as the key (primary key) for the entity Entities can only have one primary key

27. Sahar Mosleh California State University San MarcosPage 27 Entities PROJECTSUPPLIER PART EMPLOYEE LOCATION DEPARTMENT WAREHOUSE

28. Sahar Mosleh California State University San MarcosPage 28 Entities and Attributes PROJECTSUPPLIER PART LOCATIONDEPARTMENT WAREHOUSE Supplier No Supplier Name Location Project No Project Name Location Wareh. No Wareh. Name Location Part No Part Name QTYWGT City Dept. No Dept. Name Manager EMPLOYEE Emp. No Emp. Name TitleSalaryAddr

29. Sahar Mosleh California State University San MarcosPage 29 Entities, Attributes, and Relationship PROJECTSUPPLIER PART EMPLOYEE LOCATIONDEPARTMENT WAREHOUSE Supplier No Supplier Name Location Project No Project Name Budget Wareh. No Wareh. Name Location Part No Part Name QTYWGT City Dept. No Dept. Name Manager are supplied by supply are used by use works on has Emp. No Emp. Name TitleSalaryAddr Contains is contained in

30. Sahar Mosleh California State University San MarcosPage 30 All Notations Regular entity RegularKeyDerived Or Entities Attributes Relationships

31. Sahar Mosleh California State University San MarcosPage 31 Example of ERD Employee No Employee Name SalaryTitle Address PROJECT Budget Project Name Project No TotalEmp Location WORKS ON Duration Responsibility WORKS ON EMPLOYEE

32. Sahar Mosleh California State University San MarcosPage 32 Relationships A relationship logically associates two or more entities with each other Binary relationship associates two entities Ternary relationship associates three entities with each other N-ary relationship associates n entities with each other

33. Sahar Mosleh California State University San MarcosPage 33 Relationship attributes Attributes can be attached to specific relationships. Attributes that belong to two different entities should be placed as the attribute of the relationship These values provide data about the relationship between the participating entity instances. PROJECT Budget Project Name Project No EMPLOYEE Employee No Employee Name SalaryTitle Responsibility WORKS ON WORKS ON Duration

34. Sahar Mosleh California State University San MarcosPage 34 Kinds of Relationships (Cardinality) Fundamental ones are: One-to-one Many-to-one (one-to-many) Many-to-many NOTE: There can be multiple relationships between two entities WORKS-IN EMPLOYEE MANAGES DEPARTMENT

35. Sahar Mosleh California State University San MarcosPage 35 One-to-One Relationship Each instance of an entity class E1 can be associated with at most one instance of another entity class E2 and vice versa. Example : Each employee can work on at most one project and each project employs at most one employee. PROJECT Budget Project Name Project No EMPLOYEE Employee No Employee Name SalaryTitle Responsibility WORKS ON Duration 1 1

36. Sahar Mosleh California State University San MarcosPage 36 WorksOn Relationship EMPLOYEE PROJECT e1 e2 e3...... e4 p1 p2 p3...... p4 One-to-One Relationship

37. Sahar Mosleh California State University San MarcosPage 37 One-to-Many relationship Each instance of one entity class E1 can be associated with zero or more instances of another entity class E2, but each instance of E2 can be associated with at most 1 instance of E1. Example : Each employee can work on at most one project; each project can employ many employees. PROJECT Budget Project Name Project No EMPLOYEE Employee No Employee Name SalaryTitle Responsibility WORKS ON Duration N 1

38. Sahar Mosleh California State University San MarcosPage 38 WorksOn Relationship EMPLOYEE PROJECT e1 e2 e3.... e4 p1 p2 p3...... p4 e5 One-to-Many Relationship

39. Sahar Mosleh California State University San MarcosPage 39 Many-to-Many Relationship Each instance of one entity class can be associated with many instances of another entity class, and vice versa. Example : Each employee can work on many projects; each project can employ many employees PROJECT Budget Project Name Project No EMPLOYEE Employee No Employee Name SalaryTitle Responsibility WORKS ON Duration N M

40. Sahar Mosleh California State University San MarcosPage 40 WorksOn Relationship EMPLOYEE PROJECT e1 e2 e3.... e4 p1 p2 p3...... p4 e5 Many-to-Many Relationship

41. Sahar Mosleh California State University San MarcosPage 41 MANAGES 1 1 EMPLOYEEPROJECT Responsibility Duration Budget Project Name Project NoEmployee No Employee Name SalaryTitle WORKS-ON NM Multiple Relationships

42. Sahar Mosleh California State University San MarcosPage 42 Mapping ERD to Table: Step 1: For each strong entity E in the ERD Create a table T that includes all the simple attributes of E Choose one of the key attributes of E as primary key for T If the chosen key of E is composite, the set of simple attributes that form it will together form the primary key of T Example: Project (ProjectNo, ProjectName, Budget) PROJECT Budget Project Name Project No WORKS ON

43. Sahar Mosleh California State University San MarcosPage 43 Step 2: Binary one-to-one Relationship For each binary one-to-one relationship: As you did in step 1, create 2 tables T1 and T2 for entities E1 and E2 that relate to each other by one-to-one relationship. Choose one table (say T1) and include the primary key of T2 as a foreign key in T1. It is better to choose the table with total participation not the one with partial participation Include all the attributes of the relationship as attributes of T1 In Summary: Create a foreign key and move relationship attributes to any side of the one-to-one relationship

44. Sahar Mosleh California State University San MarcosPage 44 PROJECT Budget Project Name Project No EMPLOYEE Employee No Employee Name SalaryTitle Responsibility WORKS ON Duration 1 1 Table 1: EMPLOYEE (EmployeeNo, EmployeeName, Title, Salary, ProjectNo, Duration, Responsibility, ) Table 2:PROJECT (ProjectNo, ProjectName, Budget) OR Table 1: PROJECT (ProjectNo, ProjectName, Budget, EmployeeNo, Duration, Responsibility) Table 2: EMPLOYEE (EmployeeNo, EmployeeName, Title, Salary) Foreign key that references Project table Foreign key that references Employee table Example of Binary one-to-one Relationship

45. Sahar Mosleh California State University San MarcosPage 45 PROJECT Budget Project Name Project No EMPLOYEE Employee No Employee Name SalaryTitle WORKS ON MANAGES Start-Date 1 1 In this case, because PROJECT has total participation and EMPLOYEE has partial participation, it is a better idea to do the following: Table 1: PROJECT (ProjectNo, ProjectName, Budget, EmployeeNo, Start-Date) Table 2:EMPLOYEE (EmployeeNo, EmployeeName, Title, Salary) Another example of Binary one-to-one Relationship Foreign key that references Employee table

46. Sahar Mosleh California State University San MarcosPage 46 Step 3: Binary One-to-Many Relationship For each regular binary one-to-many relationship do: As you did in step 1, create 2 tables T1 and T2 for entities E1 and E2 that relate to each other by one-to-Many relationship. Identify the table that represents the participating entity at the N-side (say this table is T1) Include the primary key of T2 as foreign key in T1 Include any simple attributes of the one-to-many relationship as attributes of T1 Summary: Create a foreign key and move relationship attributes to the N-side of the one-to-many relationship

47. Sahar Mosleh California State University San MarcosPage 47 PROJECT Budget Project Name Project No EMPLOYEE Employee No Employee Name SalaryTitle Responsibility WORKS ON WORKS ON Duration N 1 Table 1: EMPLOYEE (EmployeeNo, EmployeeName, Title, Salary, ProjectNo, Duration, Responsibility) Table 2:PROJECT (ProjectNo, ProjectName, Budget) Foreign key that references Project table Example of Binary One-to-Many Relationship

48. Sahar Mosleh California State University San MarcosPage 48 Step 4: Binary Many-to-Many Relationship For each binary many-to-many relationship As you did in step 1, create 2 tables T1 and T2 for entities E1 and E2 that relate to each other by many-to-many relationship. Create a new Table T3 Include as foreign key attributes in T3 the primary keys of T1 and T2. Their combination will form the primary key of T3 Include any simple attributes of the many-to-many relationship as attributes of T3 Summary: Each many-to-many relationship becomes a table with foreign keys to the participants

49. Sahar Mosleh California State University San MarcosPage 49 PROJECT Budget Project Name Project No EMPLOYEE Employee No Employee Name SalaryTitle Responsibility WORKS ON WORKS ON Duration N M Table 1: EMPLOYEE (EmployeeNo, EmployeeName, Title, Salary) Table 2:PROJECT (ProjectNo, ProjectName, Budget) Table 3:WORKS-ON (EmployeeNo, ProjectNo, Duration, Responsibility) Foreign key that references Employee table Example of Binary Many-to-Many Relationship Foreign key that references Project table

50. Sahar Mosleh California State University San MarcosPage 50 Some Comments When you create your ERD, it is a better idea to follow the following general rules You should use the convention that entity type and relationship type names are in uppercase letters, attribute names are capitalized and role names are in lowercase letters Another naming consideration involves choosing binary relationships names to make the ERD of the schema readable from left to right and from top to bottom

51. Sahar Mosleh California State University San MarcosPage 51 Example: Given the following ERD find the corresponding tables. Flight: FlightNo, Destination Passenger: PassNo, PassName, PassAddr Fly:FlightNo, PassNo, SeatNo, Meal Baggage:BagNo, Weight, PassNo

52. Sahar Mosleh California State University San MarcosPage 52 Student Department Course Major Faculty take gives Belongs-to teach offers Can-take N 1 1 N 1 1 M N M N N M St-idSt-Name St-email semester Maj-id Maj-Name Fac-id Fac-Name Dep-id Dep-Name Dep-Location Part of the Lab 1 Question: Given the following ERD, find the corresponding tables.