Managment information system Managment information systemTutorial.
- 1. MANAGEMENT INFORMATION SYSTEMS (TUTORIAL SESSION)
- 2. Introduction to DBMS and ACID characteristics Entity-Relation diagram Normalization CONTENT
- 3. INTRODUCTION What is Data? Data is a collection of a distinct small unit of information. It can be used in a variety of forms like text, numbers, media, bytes, etc. and can be stored in pieces of paper or electronic memory, etc. In computing, Data is information that can be translated into a form for efficient movement and processing. Data is interchangeable.
- 4. What is Database? A database is an organized collection of data, so that it can be easily accessed and managed You can organize data into tables, rows, columns, and index it to make it easier to find relevant information The main purpose of the database is to operate a large amount of information by storing, retrieving, and managing data Modern databases are managed by the database management system (DBMS)
- 5. DISADVANTAGES OF FILE SYSTEM 1. Data redundancy 2. Data inconsistency 3. Difficulty in accessing data 4. Data isolation 5. Security problem 6. Atomicity problem 7. Complex access anomalies 8. Integrity problem
- 6. ACID PROPERTIES IN DBMS DBMS is the management of data that should remain integrated when any changes are done in it. It is because if the integrity of the data is affected, whole data will get disturbed and corrupted. Therefore, to maintain the integrity of the data, there are four properties described in the database management system, which are known as the ACID properties. The ACID properties are meant for the transaction that goes through a different group of tasks, and there we come to see the role of the ACID properties.
- 7. ACID PROPERTIES The expansion of the term ACID defines for:
- 8. 1) ATOMICITY The term atomicity defines that the data remains atomic. It means if any operation is performed on the data, either it should be performed or executed completely or should not be executed at all. It further means that the operation should not break in between or execute partially. In the case of executing operations on the transaction, the operation should be completely executed and not partially.
- 9. 2) CONSISTENCY The word consistency means that the value should remain preserved always. In DBMS, the integrity of the data should be maintained, which means if a change in the database is made, it should remain preserved always. In the case of transactions, the integrity of the data is very essential so that the database remains consistent before and after the transaction. The data should always be correct.
- 10. 3) ISOLATION The term 'isolation' means separation. In DBMS, Isolation is the property of a database where no data should affect the other one and may occur concurrently. In short, the operation on one database should begin when the operation on the first database gets complete. It means if two operations are being performed on two different databases, they may not affect the value of one another. In the case of transactions, when two or more transactions occur simultaneously, the consistency should remain maintained. Any changes that occur in any particular transaction will not be seen by other transactions until the change is not committed in the memory.
- 11. If two operations are concurrently running on two different accounts, then the value of both accounts should not get affected. The value should remain persistent. As you can see in the below diagram, account A is makingT1 andT2 transactions to account B and C, but both are executing independently without affecting each other. It is known as Isolation.
- 12. 4) DURABILITY Durability ensures the permanency of something. In DBMS, the term durability ensures that the data after the successful execution of the operation becomes permanent in the database. The durability of the data should be so perfect that even if the system fails or leads to a crash, the database still survives. However, if gets lost, it becomes the responsibility of the recovery manager for ensuring the durability of the database. For committing the values, the COMMIT command must be used every time we make changes.
- 13. ER DIAGRAM IN DBMS ER model stands for an Entity-Relationship model. This model is used to define the data elements and relationship for a specified system. It develops a conceptual design for the database. It also develops a very simple and easy to design view of data. In ER modeling, the database structure is portrayed as a diagram called an entity-relationship diagram.
- 14. ER DIAGRAM IN DBMS A non-technical design method that works on conceptual level based on the perception of real world Consists of collection of basic objects called entities and of relationship among objects and attributes which define their properties Free from ambiguities and provides a standard and logical way of visualizing data Thus, it is a diagrammatic representation which is easy to understand by non-technical user
- 15. ENTITY RELATIONSHIP DIAGRAM Notation – Crow’s foot
- 16. WHAT IS AN ENTITY IN ERDS? An entity simply represents an object in our database.This could be an object for users, courses, products, and so on. Note that the name of every entity should be singular (user) and not plural (users). Here is what an entity looks like: The diagram above shows an entity called user. This entity will have information about the various users registered on a platform.
- 17. WHAT ARE ATTRIBUTES IN ERDS? The information about an object is the attributes. We can say the properties of an entity are the attributes. The entity in the diagram above has three attributes – username,age, and email.
- 18. RELATIONSHIP BETWEEN ENTITIES IN ERDS In most cases, databases are made up of more than one entity. To understand the relationship between one entity and another, we use lines to connect them. But these lines have notations (indicators) on them to specify the type of relationship that exists between two entities. We'll use crow's foot notation to specify our entity relationships.
- 19. SYMBOLS IN CROW’S FOOT NOTATION ANDTHEIR MEANING Cardinality acts as a parameter for the relationship between entities. For one entity, there is a minimum and maximum number that helps define its relationship with another entity. Zero o The symbol/diagram above denotes zero in crow's foot notation. o We know this because the of the zero/circle indicator at the right side of the horizontal line.
- 20. One o The diagram above shows a horizontal line with a short vertical lines crossing it. o The vertical line acts as the indicator – it denotes one. Many o The diagram above denotes many. o You can easily remember this symbol because it looks like a crow's foot.
- 21. Zero or Many o The zero or many symbol/indicator in crow's foot notation is a combination of the zero and many indicators. One or Many o The one or many indicator is a combination of two indicators – one and many. One and only one o The one and only one indicator has two "one" indicators.
- 22. CROW'S FOOT NOTATION EXAMPLE #1 Let's assume we have two entities in our database: A teacher and course entity.
- 23. Relationship of theTeacher Entity and the Area Course Entity Each teacher can only teach one area course. The notation here will be one and only one The minimum number of courses a teacher can take up is one, and the maximum is also one.
- 24. Relationship of the Area Course Entity and theTeacher Entity One area course can be taught by one or many teachers. The minimum here will be one while the maximum will be many. The notation to be used is one or many.
- 25. CROW'S FOOT NOTATION EXAMPLE #2 The notations don't always have to be different. What matters is the logic behind the relationship between entities. This is entirely up to the those creating or designing the database.
- 26. INTERPRETATION The notation on the left has the zero or many notation. This implies that a pizza can be ordered by none (optional) or many customers. Similarly, the notation on the right side implies that a customer can order zero or many pizzas. The cardinality here is the same for both entities. Zero is the minimum while many is the maximum.
- 27. NOTATION OF ER DIAGRAM Database can be represented using the notations. In ER diagram, many notations are used to express the cardinality. These notations are as follows
- 28. FUNCTIONAL DEPENDENCY The functional dependency is a relationship that exists between two attributes in a tableT : X → Y The left side of FD is known as a determinant, the right side of the production is known as a dependent. For example: Assume we have an employee table with attributes: Emp_Id, Emp_Name,Emp_Address. Here Emp_Id attribute can uniquely identify the Emp_Name attribute of employee table because if we know the Emp_Id, we can tell that employee name associated with it. Functional dependency can be written as: Emp_Id → Emp_Name We can say that Emp_Name is functionally dependent on Emp_Id.
- 29. FUNCTIONAL DEPENDENCY VS FULLFUNCTIONAL DEPENDENCY Let X and Y be sets of attributes in a table T 🞐 Y is functionally dependent on X in T iff for each set x R.X there is precisely one corresponding set y R.Y 🞐 Y is fully functional dependent on X in T if Y is functional dependent on X and Y is not functional dependent on any proper subset of X
- 30. EXAMPLE Book table Author attribute is: functionally dependent on the pair { BookNo, Title} fully functionally dependent on BookNo
- 31. EXAMPLE table BorrowedBooks Address attribute is functionally dependent on the pair { BookNo, Patron} fully functionally dependent on Patron
- 32. PROBLEMS Cannot insert new patrons in the system until they have borrowed books ■ Insertion anomaly 🞐 Must update all rows involving a given patron if he or she moves. ■ Update anomaly 🞐 Will lose information about patrons that have returned all the books they have borrowed ■ Deletion anomaly
- 33. TYPES OF FUNCTIONAL DEPENDENCY
- 34. 1.TRIVIAL FUNCTIONAL DEPENDENCY A → B has trivial functional dependency if B is a subset of A. The following dependencies are also trivial like:A → A, B → B Example: Consider a table with two columns Employee_Id and Employee_Name {Employee_id, Employee_Name} → Employee_Id is a trivial functional dependency as Employee_Id is a subset of {Employee_Id,Employee_Name} Also, Employee_Id → Employee_Id and Employee_Name → Employee_Name are trivial dependencies too.
- 35. 2. NON-TRIVIAL FUNCTIONAL DEPENDENCY A → B has a non-trivial functional dependency if B is not a subset of A. When A intersection B is NULL, then A → B is called as complete non-trivial. Example: ID → Name, Name → DOB
- 36. KEYS Key is used to uniquely identify any record or row of data from the table. It is also used to establish and identify relationships between tables. For example, ID is used as a key in the Student table because it is unique for each student. In the PERSON table, passport_number, license_number, SSN are keys since they are unique for each person.
- 37. 1. SUPER KEY Super key is an attribute set that can uniquely identify a tuple. A super key is same as candidate key.
- 38. 2. CANDIDATE KEY A candidate key is an attribute or set of attributes that can uniquely identify a tuple. For example: In the EMPLOYEE table, id is best suited for the primary key. The rest of the attributes, like SSN, Passport_Number, License_Number, etc., can also be considered a candidate key.
- 39. 3. PRIMARY KEY It is the first key used to identify one and only one instance of an entity uniquely. An entity can contain multiple keys, as we saw in the PERSON table. The key which is most suitable from those lists becomes a primary key. In the EMPLOYEE table, ID can be the primary key since it is unique for each employee. In the EMPLOYEE table, we can even select License_Number and Passport_Number as primary keys since they are also unique. For each entity, the primary key selection is based on requirements and developers.
- 40. NORMALIZATION Normalization is the process of organizing the data in the database. Normalization is used to minimize the redundancy from a relation or set of relations. It is also used to eliminate undesirable characteristics like Insertion, Update, and Deletion Anomalies. Normalization divides the larger table into smaller and links them using relationships. The normal form is used to reduce redundancy from the database table.
- 41. WHY DOWE NEED NORMALIZATION? The main reason for normalizing the relations is removing anomalies. Failure to eliminate anomalies leads to data redundancy and can cause data integrity and other problems as the database grows. Normalization consists of a series of guidelines that helps to guide you in creating a good database structure.
- 42. Data modification anomalies can be categorized into three types: Insertion Anomaly: Insertion Anomaly refers to when one cannot insert a new tuple into a relationship due to lack of data. Deletion Anomaly:The delete anomaly refers to the situation where the deletion of data results in the unintended loss of some other important data. Update Anomaly:The update anomaly is when an update of a single data value requires multiple rows of data to be updated.
- 43. DESIGNING DATABASES ⮚ Schema – the logical structure of the database e.g., the database consists of information about a set of customers and accounts and the relationship between them ⮚ Physical schema: database design at the physical level ⮚ Logical schema: database design at the logical level ⮚ State (or Instance) – the actual content of the database at a particular point in time
- 44. EXAMPLE OF A DATABASE SCHEMA
- 45. EXAMPLE OF A DATABASE STATE
- 46. TYPES OF NORMAL FORMS
- 47. Normal Form Description 1NF A relation is in 1NF if it contains an atomic value. 2NF A relation will be in 2NF if it is in 1NF and all non-key attributes are fully functional dependent on the primary key. 3NF A relation will be in 3NF if it is in 2NF and no transition dependency exists.
- 48. FIRST NORMAL FORM (1NF) A relation will be 1NF if it contains an atomic value. It states that an attribute of a table cannot hold multiple values. It must hold only single-valued attribute. First normal form disallows the multi-valued attribute, composite attribute, and their combinations.
- 49. EXAMPLE EMPLOYEE table: Relation EMPLOYEE is not in 1NF because of multi-valued attribute EMP_PHONE. EMP_ID EMP_NAME EMP_PHONE EMP_STATE 14 Rajat 7272826385, 9064738238 UP 20 Harish 8574783832 Bihar 12 Sameer 7390372389, 8589830302 Punjab
- 50. The decomposition of the EMPLOYEE table into 1NF has been shown below: EMP_ID EMP_NAME EMP_PHONE EMP_STATE 14 John 7272826385 UP 14 John 9064738238 UP 20 Harry 8574783832 Bihar 12 Sam 7390372389 Punjab 12 Sam 8589830302 Punjab
- 51. EXAMPLE For an airline
- 52. 1NF SOLUTION
- 53. EXAMPLE For a library
- 54. SECOND NORMAL FORM A table is in 2NF iff ■ It is in 1NF and ■ no non-prime attribute is dependent on any proper subset of any candidate key of the table A non-prime attribute of a table is an attribute that is not a part of any candidate key of the table A candidate key is a minimal superkey
- 55. SECOND NORMAL FORM (2NF) In the 2NF, relational must be in 1NF. In the second normal form, all non-key attributes are fully functional dependent on the primary key Example: Let's assume, a school can store the data of teachers and the subjects they teach. In a school, a teacher can teach more than one subject. TEACHER table TEACHER _ID SUBJECT TEACHER _AGE 25 Chemistry 30 25 Biology 30 47 English 35 83 Math 38 83 Computer 38
- 56. In the given table, non-prime attributeTEACHER_AGE is dependent on TEACHER_ID which is a proper subset of a candidate key.That's why it violates the rule for 2NF. To convert the given table into 2NF, we decompose it into two tables: TEACHER_DETAIL table: TEACHER_SUBJECT table: TEACHER_ID TEACHER_AGE 25 30 47 35 83 38 TEACHER_ID SUBJECT 25 Chemistry 25 Biology 47 English 83 Math 83 Computer
- 57. EXAMPLE Library allows patrons to request books that are currently out
- 58. EXAMPLE 🞐 Candidate key is {BookNo, Patron} 🞐 We have ■ Patron → PhoneNo 🞐 Table is not 2NF ■ Potential for 🞐 Insertion anomalies 🞐 Update anomalies 🞐 Deletion anomalies
- 59. 2NF SOLUTION Put telephone number in separate Patron table
- 60. THIRD NORMAL FORM (3NF) 🞐 A table is in 3NF iff ■ it is in 2NF and ■ all its attributes are determined only by its candidate keys and not by any non-prime attributes
- 61. EXAMPLE We have a table representing orders in an online store Each row represents an item on a particular order Primary key is {Order, Product} Columns Order Product Quantity UnitPrice Customer Address
- 62. FUNCTIONAL DEPENDENCIES 🞐 Each order is for a single customer ■ Order Customer 🞐 Each product has a single price ■ Product UnitPrice 🞐 Each customer has a single address ■ Customer Address
- 63. 2NF SOLUTION (II) 🞐 Decomposition ■ First table ■ Second table ■ Third table Order Product Quantity Order Customer Address Product UnitPrice
- 64. 3NF 🞐 In second table ■ Customer Address 🞐 Split second table into Order Customer Address Order Customer Customer Address
- 65. NORMALISATION 1NF: ■ {Order, Product, Customer, Address, Quantity, UnitPrice} 2NF: ■ {Order, Customer, Address}, {Product, UnitPrice}, and {Order, Product, Quantity} 3NF: ■ {Product, UnitPrice}, {Order, Product, Quantity}, {Order, Customer}, and {Customer, Address}
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