Institute of Southern Punjab, Multan

Transcription

1 Institute of Southern Punjab, Multan Mr. Muhammad Nouman Farooq BSC-H (Computer Science) MS (Telecomm. and Networks) Honors: Magna Cumm Laude Honors Degree Gold Medalist! Blog Url: noumanfarooqatisp.wordpress.com

2 Grading Policy Classification Assignments & Quizzes 6% (6 Marks in Total) Project & Presentation 9% (9 Marks) Midterm Exams 25% (25 Marks) Final Exam 50% (50 Marks) Total 100 % NOTE: 10% Marks will be Automatically given by Examination Deptt. on Attendance. 2

3 Academic Honesty Your work in this class must be your own If students are found to have collaborated excessively or to have cheated (e.g. by copying or sharing answers during an examination), all involved will at a minimum receive grades of 0 for the first violation Further violations will result in failure in the course 3

4 Few Things to Remember!! Attendance will be taken with in 15 minutes at the start of class Students are allowed to enter into class with in 30 minutes at the starting of class Zero tolerance policy on attendance, discipline of class during lectures! Assignments must be submitted on time, no late submissions In case of copied assignment both parties will be given zero! Projects, Presentation, Quizzes, Assignments, Class participation are very important. Don t miss your Classes, Quizzes, Presentations, Assignments and Projects! 4

5 Advance Database Systems Overview of RDBMS Lecture# 1 5

6 Recommended Books/Manuals Modern Database Management - 8th Edition by Jeffery A. Hoffer, Prescott and McFadden Fundamentals of Database Systems, By R. Elmasri and S. Navathe, 6th Edition, 2011 Database Systems-A Practical Approach to Design, Implementation and Management by Thomas Connolly and Carolyn BEGG, 4th Edition Database Systems Design, Implementation, and Management-Carlos, Steven and Peter (9th Edition) A Guide To MySQL 8th Edition by Philip J. Pratt & Mary Z. Last A guide to Advance MySQL latest Edition by Muhammad Nouman Farooq 6

7 Lecture 1: Overview of RDBMS Database Definitions and Advantages of RDBMS Hierarchical Structure of DBMS Introduction to File Processing Systems Advantages of Database Approach System Development Life Cycle (SDLC) Database Development Process (DDP) The Three-Level ANSI-SPARC Architecture Relational Data Structure Relational Keys 7

8 Jonathan Abrams Friendster fails due to not optimized and efficient Database System Mark Zuckerberg Facebook did not fail due to optimized and efficient Database System 8

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10 Database Definitions and Advantages of RDBMS 10

11 Database Definitions An organized collection of information in computerized format. A collection of information organized and presented to serve a specific purpose 11

12 Continued The term database is often incorrectly referred to as a synonym for a database management system (DBMS). 12

13 Continued Each of the above given definition are correct, and describe database from slightly variant perspectives. From exam point of view, anyone will do. However, within this course, we will be referring first of the above definitions more frequently, and concepts discussed in the definition like, logically related data, shared collection should be clear. 13

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15 Data and Information Data is the collection of raw facts collected from any specific environment for a specific purpose. Data in itself does not show anything about its environment, so to get desired types of results from the data we transform it into information by applying certain processing on it. Once we have processed data using different methods; than data is converted into meaningful form and that form of the Data is called information. 15

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17 Continued If we consider the data in the previous figure without the titles or the labels associated with the data (EmpName, age, salary) then; it is not much useful. However, after attaching these labels it brings some meanings to us, this meaningfulness is further increased when we associate some other labels, like the company name and the department name etc. So this is a very simple example of processing that we can do on the data to make it information. 17

18 Continued 18

19 Database Systems The term database system is a combination of database and the Database Management System (DBMS). So, database is collection of meaningful data/information, DBMS is a tool to manage this data, and both jointly are called database system. 19

20 Why Use Models? Models can be useful when we want to examine or manage part of the real world. The costs of using a model are often considerably lower than the costs of using or experimenting with the real world itself. Examples: Network Model Simulation for an Organization in Packet Tracer World Map ERD for Relational Database Systems 20

21 Hierarchical Structure of DBMS 21

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39 Flat File Vs Relational Database System 39

40 Flat File Vs Relational Database System A flat file database is a database designed around a single table. The flat file design puts all database information in one table, or list, with fields to represent all parameters. A flat file may contain many fields, often, with duplicate data that are prone to data corruption. 40

41 Continued If you decide to merge data between two flat files, you need to copy and paste relevant information from one file to the other. There is no automation between flat files. If you have two or more flat files that contain client addresses, for example, and a client moved, you would have to manually modify the address parameters in each file that contains that client s information. 41

42 Relational Database System A relational database, on the other hand, incorporates multiple tables with methods for the tables to work together. The relationships between table data can be ordered, merged and displayed in database forms. These tables are to be normalized up to 3 rd Normal Form (3-NF). 42

43 Introduction to File Processing Systems 43

44 File Processing System 44

45 File Processing System 45

46 File Processing System 46

47 Continued 47

48 Advantages of Database Approach 48

49 Database System Environment It will be helpful to reiterate our database definition here, that is, Database is a shared collection of logically related data, designed to meet the information needs of multiple users in an organization A typical database system environment is shown in the figure on next slide. 49

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51 Continued The figure shows different subsystem or applications in an educational institution, like library system, examination system, and registration system. There are separate, different application programs for every application or subsystem. However, the data for all applications is stored at the same place in the database and all application programs, relevant data and users are being managed by the DBMS. 51

52 1-Data Sharing The data for different applications or subsystems is placed at the same place. This introduces the major benefit of data sharing. That is, data that is common among different applications need not to be stored repeatedly, as was the case in the file processing environment. For example, all three systems of an educational institution shown in figure need to store the data about students. 52

53 Continued Now the data like registration number, name, address, father name that is common among different applications is being stored repeatedly in the file processing system environment, where as it is being stored just once in database system environment and is being shared by all applications. 53

54 2-Data Independence Data and programs are independent of each other, so change is one has no or minimum effect on other 3-Controlled Redundancy Means that we do not need to duplicate data unnecessarily; we do duplicate data in the databases, however, this duplication is deliberate and controlled. 54

55 4-Data Integrity: Very important feature; means the validity of the data being entered in the database. Since the data is being placed at a central place and being managed by the DBMS, so it provides a very helpful to check or ensure that the data being entered into the database is actually valid. We can also define it as Level of Correctness of Data. 55

56 5-Better Data Security All application programs access data through DBMS, So DBMS can very efficiently check that which user is performing which action and accessing which part of data. So, A DBMS is the most effectively control and maintain security of Data stored in a database. 56

57 6-Faster Development of new Applications The database environment allows us faster application development because of its many reasons. As we know that database is designed focusing the conclude result to meet the expectations of the client. 57

58 7-Better Concurrency Control Concurrency means the access of database form as number of points simultaneously. Concurrency Control means to access the database in such a way that all the data accesses are completed correctly and transparently. One example of controlled concurrency is the use of ATM Machine for withdrawal of money (cash). All ATM machines of a bank are interconnected to a central database system worldwide, so that a user can access its account from anywhere in the world and can get cash from any ATM terminal. 58

59 Continued As there are thousands of ATM terminal across the world for a specific bank so as a result thousands of user process and access the bank s database. All this process is managed concurrently using the database systems and is done in such an efficient manner that no two user face any delay in the processing of their requests. 59

60 8-Better Backup and Recovery Facility Some time happens that a database which was in use and very important transactions were made after the last backup was made, all of a sudden due to any disastrous situation the database crashes (improper shutdown, invalid disk access, etc.) Now, In such a situation the database management system should be able to recover the database to a consistent state so that the transactions made after the last backup are not lost. 60

61 System Development Life Cycle (SDLC) 61

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64 Database Development Process (DDP) 64

65 Database Development Process Database Application development Process includes the Following Stages or steps: 1. Preliminary Study 2. Requirement Analysis 3. Database Design 4. Physical Design 5. Implementation 6. Maintenance 65

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67 Preliminary Study Design of database is carried out in a number of steps; these steps play important role in the design process and need to be given proper attention. First Phase of the database development process is the Preliminary Study, which is based on the proper study of the system. It means that all the parts of the systems, or the section of the subject organization for which we intend to develop the system must be studied. 67

68 Continued We should find the relation or interaction of different section of the organization with each other and should understand the way information flows between different sections of the organization. Moreover it should also be made clear that what processing is performed at each stage of the system. 68

69 Requirement Analysis Once we have investigated the organization for its different sections and the way data flows between those sections; Detailed study of the system is started to find out the requirements of each section. In second phase, The detailed study of the system and its functionality decisions made at this stage decide the overall activity of the organization. Requirements of one section of the organization are fulfilled in such a way that all the sections in the organization are supporting each other. For example we can say that the results produced by the processing taking place at one section are used as input for another section. 69

70 Database Design Third phase in the database development process is the database design. This is a technical phase of the process and need handsome skill as a Database Administrator. This is the phase where the conceptual design of the database is created. It also known as Conceptual Data Modeling. Entities are identified and given attributes, relationships are built and different types of relationship are performed by assigning cardinalities. 70

71 Physical Design In fourth phase, The choice of the DBMS is made on the basis of requirements and the environment in which the system will operate. Implementing a database on a specific DBMS is very important because it involves the major financial investment of the organization, and can not be reverted in case a selected DBMS in not capable of providing the desired efficiency. Also, Assigning meaningful Data Types, Constraints/Limitations and De-Normalization of Data where required by the real time scenario/system are to be finalized and processed in this phase. 71

72 Implementation This phase is specific to writing the application programs needed to carry out different activities according to user requirements. We must write application programs in this phase by using MySQL (mai-structured query language) by using DBMS engine known as XAMPP (Cross platform apache MySequel PHP Perl). We can done coding with out any logical error; If we have implemented all previous phases of database development process correctly. 72

73 Maintenance Maintenance means to fine tune the system and check that the designed applications systems are fulfilling the purpose for which they are meant. Also, this phase may involve designing any new application for the enhancement of the system. Or an already working application may need to be updated or modified to remove any errors or to add some functionality in the system. 73

74 Continued All these stages are necessary and must be given the necessary attention at each level to get properly working and good system design and a better working environment. 74

75 The Three-Level ANSI-SPARC Architecture 75

76 Three Level ANSI-SPARC Architecture The levels form a three-level architecture comprising an External, Conceptual, and an Internal level. The way users observe the data is called the External Level (Front End). The way the DBMS and the Operating System perceive/stores the data (Back End) is the Internal Level. The Conceptual Level provides both the mapping and the desired independence between the external and internal levels. 76

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79 Continued The overall Description/Skeleton structure of the database is called the database schema. At the highest level, we have multiple external schemas (also called subschemas) that correspond to different views of the data. At the conceptual level, we have the conceptual schema, which describes all the entities, attributes, and relationships together with integrity constraints. At the lowest level, we have the internal schema, which is a complete description of the internal model, containing the definitions of stored records, the methods of representation, the data fields, and the indexes and storage structures used. There is only one conceptual schema and one internal schema per database. 79

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81 Continued The objective of the three-level architecture is to separate each user s view of the database from the way the database is physically represented. There are several reasons why this separation is desirable:- 1. Each user should be able to access the same data, but have a different customized view of the data. 2. Users should not have to deal directly with physical database storage details. 81

82 Continued 4. The internal structure of the database should be unaffected by changes to the physical aspects of storage, such as the changeover to a new storage device. 5. The Database Administrator (DBA) should be able to change the conceptual and database storage structures without affecting the users views. 82

83 Continued A major objective for the three-level architecture is to provide data independence, which means that upper levels are unaffected by changes to lower levels. There are two kinds of data independence: - 1. Logical Data Independence. 2. Physical Data Independence. 83

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85 Continued 1. Logical Data Independence: - Changes to the conceptual schema, such as the addition or removal of new entities, attributes, or relationships, should be possible without having to change existing external schemas or having to rewrite application programs. Clearly, the users for whom the changes have been made need to be aware of them, but what is important is that other users should not be. 85

86 Continued 2. Physical Data Independence: - Changes to the internal schema, such as using different file storage structures, using different storage devices should be possible without having to change the conceptual or external schemas. 86

87 Relational Data Structure 87

88 Relational Data Structure 88

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91 Relational Keys 91

92 Relational Keys Keys are used to create relationship among different database tables. An entity type may have many instances, from a few to several thousands and even more. Now out of many instances, when and if we want to pick a particular/single instance, and many times we do need it, then key is the solution. For example, think of whole population of Pakistan, the data of all Pakistanis lying at one place, say with NADRA people. Now if at sometime we need to identify a particular person out of all this data, how can we do that? 92

93 Continued While defining an entity; we also generally define the key of that entity. How do we select the key, from the study of the real-world system; key attribute(s) already exist there, sometimes they don t automatically enabled; then the designer has to define one. A key can be simple, that is, consisting of single attribute, or it could be composite which consists of two or more attributes. 93

94 Super Key 94

95 Candidate Key A super key for which no subset is a super key is called a candidate key, or the minimal super key is the candidate key. It means that there are two conditions for the candidate key, One; It identifies the entity instances uniquely, as is required in case of super key, Second; It should be minimum, that is, no proper subset of candidate key is a key. 95

96 Continued So, If we have a simple super key, that is, that consists of single/simple attribute, it is definitely a candidate key, 100%. However, if we have a composite super key and if we take any attribute out of it and remaining part is not a super key anymore then that composite super key is also a candidate key since it is minimal super key. For example, one of the super keys that we identified from the entity STUDENT is regno, name, this super key is not a candidate key, since if we remove the regno attribute from this combination, name attribute alone is not able to identify the entity instances uniquely. 96

97 Primary Key A candidate key chosen by the database designer to act as key is the primary key. An entity type may have more than one candidate keys, in that case the database designer has to designate one of them as primary key, since there is always only a single primary key in an entity type. If there is just one candidate key then obviously the same will be declared as primary key. The primary key can also be defined as the successful candidate key. 97

98 Continued The relation that holds between super and candidate keys also holds between candidate and primary keys, that is, every primary key (PK) is a candidate key and every candidate key is a super key. A certain value that may be associated with any attribute is NULL, that means not given or not defined. A major characteristic of the Priamary Key is that it cannot have the NULL value. 98

99 Unique Key A candidate key which can return a Record uniquely but may store a NULL value is called as Unique Key. stdcontactnumber attribute in STUDENT table is known as Unique key. 99

100 Alternate Key Candidate keys which are not chosen as the primary key are known as alternate keys. For example, we have two candidate keys of EMPLOYEE in figure 2, regno and nidnumber, if we select regno as PK then the nidnumber will be alternate key. 100

101 Foreign Key Sometimes the information stored in a relation is linked to the information stored in another relation. If one of the relations is modified, the other must be checked, and perhaps modified, to keep the data consistent. 101

102 Continued Suppose that in addition to Students, we have a second relation: Enrolled (cid: string, sid: string, cgrade: Text) The sid field of Enrolled is called a foreign key and refers to Students. The foreign key in the referencing relation (Enrolled, in our example) must match the primary key of the referenced relation (Students), i.e., it must have the same number of columns and compatible data types, although the column names can be different. 102

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104 Continued As the figure shows, there may well be some students who are not referenced from Enrolled (e.g., the student with sid=50000) However, every sid value that appears in the instance of the Enrolled table appears in the primary key column of a row in the Students table. 104

105 Continued If we try to insert the tuple (55555, Art104, A) into E1, the rule is violated because there is no tuple in S1 with the id 55555; the database system should reject such an insertion. Similarly, if we delete the tuple (53666, Jones, 18, 3.4) from S1, we violate the foreign key constraint because the tuple (53666, History105, B) in E1 contains sid value 53666, the sid of the deleted Students tuple. The DBMS should disallow the deletion or, perhaps, also delete the Enrolled tuple that refers to the deleted Students tuple. 105

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107 Secondary Key Many times we need to access certain instances of an entity type using the values of one or more attributes other than the PK. The difference in accessing instances using the value of a key or non-key attribute is that the search on the value of PK will always return a single instance (if it exists), where as uniqueness is not guaranteed in case of non-key attribute. 107

108 Continued Such attributes on which we need to access the instances of an entity type that may not necessarily return unique instance is called the secondary key. For example, we want to see how many of our students belong to Multan, in that case we will access those instances of the STUDENT entity type that contain Multan in their address. 108

109 Continued In this case address will be called secondary key, since we are accessing instances on the basis of its value, and there is no compulsion that we will get a single instance. Keep one thing in mind here, that a particular access on the value of a secondary key MAY return a single instance, but that will be considered as chance. 109

110 Continued There is not the compulsion or it is not necessary for secondary key to return unique instance But; In case of super, candidate, primary and alternate keys it is compulsion that they will always return unique instance against a particular value. 110

111 Surrogate Key: A Surrogate Key is any column or set of columns that can be declared as the primary key instead of more than two composite Primary keys that jointly makes a Cumbersome key (CUMBERSOME meaning: Large Set). Example of Cumbersome key and Surrogate key is shown in next slide.

112 Continued b) Mapping the ternary relationship PATIENT TREATMENT Remember that the primary key MUST be unique This is why treatment date and time are included in the composite primary key But this makes a very Cumbersome Key It would be better to create a Surrogate Key like treatmentid in PATIENT_TREATMENT table 112

113 Quick Review of Relational Keys Concept s Every Candidate Key must be a Super Key. But, Every Super Key may not be a Candidate Key. Every Primary Key must be a Candidate Key. But, Every Candidate key may not be a Primary Key. Every Alternate Key must be a Candidate Key. But, Every Candidate key may not be a Alternate Key. Every Foreign Key must be a Primary Key. Every Secondary Key must not be a Candidate Key & Primary Key & Alternate Key. Cumbersome Key (Group of Composite Primary Keys) can be replaced by Surrogate Key 113

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116 Recommended Readings Chapter 1 from: - Database Systems-A Practical Approach to Design, Implementation and Management by Thomas Connolly and Carolyn BEGG, 4th Edition (Page No ) Modern Database Management - 8th Edition by Jeffery A. Hoffer, Prescott and McFadden (Page No ) 116

117 Chapter 2 from: - Continued Modern Database Management 8 th Edition by Jeffery A. Hoffer, Prescott and McFadden (Page No ) Database Systems-A Practical Approach to Design, Implementation and Management by Thomas Connolly and Carolyn BEGG, 4 th Edition (Page No ) Fundamentals of Database Systems 6 th Navathe (Page No ) Edition by Elmasri and 117

118 Continued Chapter 5 from: Modern Database Management 8 th Edition by Jeffery A. Hoffer, Prescott and McFadden (Page No ) Chapter 3 from: Database Systems-A Practical Approach to Design, Implementation and Management by Thomas Connolly and Carolyn BEGG, 4 th Edition (Page No ) 118

119 Summary of Lecture Lecture 1 Database Definitions and Advantages of RDBMS Hierarchical Structure of DBMS Introduction to File Processing Systems Advantages of Database Approach 119

120 Summary of Lecture (Continued..) Lecture 1 System Development Life Cycle (SDLC) Database Development Process (DDP) The Three-Level ANSI-SPARC Architecture Relational Data Structure Relational Keys 120

121 END OF LECTURE 1 121