Lecture 7 - Database Management Systems PDF

‫المحاضرة السابعة‬ ‫الجامعة األسمرية اإلسالمية‬ ‫كلية العلوم زليتن‬ ‫‪ ‬القسم العلوم الطبية ‪‬‬ ‫(الفصل االول للسنة التمهيدية )‬ ‫علوم الحاسـوب‬ ‫د‪.‬ايمن مختار ارميص‬ ‫أ‪.‬صالح الهادي جوان‬ ‫أ‪.‬مفتاح محمد الكزاغلي‬ ‫أ‪.‬عبدهللا مسعود االرقط‬ ‫`‬ ‫ال...

‫المحاضرة السابعة‬ ‫الجامعة األسمرية اإلسالمية‬ ‫كلية العلوم زليتن‬ ‫‪ ‬القسم العلوم الطبية ‪‬‬ ‫(الفصل االول للسنة التمهيدية )‬ ‫علوم الحاسـوب‬ ‫د‪.‬ايمن مختار ارميص‬ ‫أ‪.‬صالح الهادي جوان‬ ‫أ‪.‬مفتاح محمد الكزاغلي‬ ‫أ‪.‬عبدهللا مسعود االرقط‬ ‫`‬ ‫العام الجامعـي ‪2024—2023‬م‬ ‫‪1‬‬  Data Base & Data Base Management System Database (DB). It is a set of data and information stored in a typical manner and without repetition and related to each other according to mutual relationships. A database consists of one or more tables. The table consists of a record (Record) or more than one record, and the record consists of a (Field) field or more than one field. There is a key field (PK), which is a value that uniquely identifies each record in the file. An example of a record: the record of a specific employee consists of From several fields such as the employee number - the employee's name - the employee's grade - the date of appointment - the salary - and the department he belongs to...etc. The employee's data is stored in the computer in an organized manner. Likewise, the relationships between these tables are determined according to specific and fixed bases that depend on the work rules in this system, as well as on the correct methods for designing databases. And the databases are separated from the programs that process this data. Such as entry, modification, and deletion programs, and databases are managed by a system called a database management system. (Database Management system) Data is retrieved using commands from a query language, as it is considered information that helps in the decision-making process. Fundamental Database Concepts 1-Data Data is the primary raw material of information 2- Information It is the output of data processing, analysis or synthesis, in order to extract what it contains or what it refers to in terms of indicators, signs, and others. 3-Record A record is the place (row) in which the integrated data for one of the cases of the subject of the table is stored 2 Example: such as all the personal data of a specific person (name, address, phone….). 4- The relationship between the statement and the information Data -> Processing -> Information File or Table A file or table is a container that contains data about a subject and stores it in order to retrieve it when it is needed. 5-Field The field is the place (column) in which one statement of table data is stored (type - name...) Example: such as the statement for (person's name - person's address -..). 6- keys 1-Primary or primary key (PK) It is a column (or more) of the table that distinguishes the records from each other, in which the values are unique (non-repeated) and cannot contain a value (its value is NULL), and the table has a single primary key. 2- FOREIGN KEY(FK) A column (or more) of a table that can be considered a reference to another column in a second table (usually this column is the primary key of the second table). 3 Definition of a database management system (DBMS) It is a group of programs that manage and control the process of storing and retrieving data, as well as providing the ability for a large number of users to access and deal with the database. It is seen as a link between users and the database, as it receives user requests and then transfers them to a database. The data and implementation of the programs necessary to implement these requirements and then provide the user with the required results. Such as: Oracle, Microsoft Access, SQL Server, MS Access. There is a goal of the database management system from the administrative point of view, which is to assist in planning and decision-making. A comparison must be made between the database, which consists of a group of files linked together, and the database management system, which represents a set of software that efficiently manages a set of interrelated data. Data management is an organizational function for the management of the data resource, which is responsible for creating an information policy and procedures for securing information with standard quality, which makes data managed as an organizational resource. It also includes developing information policies, planning data, designing databases, and developing a dictionary. Database functions: A- Adding a new information or statement to the file. B- Delete old data that is no longer needed. C- Changing existing data according to new information. D- Searching and inquiring about specific information or information. E- Arranging and organizing the data inside the files. F- Presentation of data in the form of reports or organized forms. G- Calculating the final sum, subtotal, or arithmetic average of the required data. Advantages of database systems: due to its support on the principle of collecting data in one location, provides centralized control over the data, which helps to avoid the weaknesses of traditional file systems, and among the advantages: 4 1. The possibility of reducing unjustified repetition of data: data replication means storing the same data in more than one place, and the use of databases has reduced this problem. 2. The possibility of avoiding data differences: If the data is stored in more than one file and distributed in more than one location, this may lead to a modification to the data in one of these locations and the same data remaining unchanged in the other locations, which causes inconsistency in the data pertaining to certain fact. 3. Achieving the principle of data sharing: it means allowing more than one user to access the data in the database at the same time. 4. The possibility of applying security and confidentiality restrictions: Data security is intended to protect it from illegal entry or loss, and data security is an important feature of database management systems. 5. Keeping data integrity: It is intended to set check and audit points to avoid incorrect or unreasonable entry or update, in addition to ensuring that there is no conflict in the stored data. 6. The possibility of applying the principle of independence: which is the ability to make changes in the data structure without making changes in the programs that operate on the data. Components of a database system The database system consists of four basic components: 1 - Data: Databases are available on small and personal computers as well as on large computers, and the efficiency of the system depends on the ability and capabilities of the computer’s automated entity. Personal computers provide a database for one user, while large computers provide a database for a number of users who share on the available data. 2 - Equipment: The databases depend heavily on magnetic disks as well as on dense tape units as backup units for emergency data storage. 3 - Programs: 5 It is the intermediate layer between the data stored in the files on top of the disks and between the users of the database. 4 - Database users : They are divided into three categories: Software planners who write their programs and use the capabilities of the database. Database specialists, who are responsible for maintaining and operating the database. Database users who interact with the database via terminals. Database models Many database models have appeared, the most important of which are: Hierarchical Database Model In a hierarchical database model, data is organized into a hierarchy of records, with the topmost record being the root of the hierarchy. Each record in the hierarchy can have one or more child records, which are linked to the parent record. This allows for the representation of data relationships and the efficient retrieval of data. Hierarchical Database Advantages 1. Fast and efficient data retrieval: One of the key advantages of hierarchical databases is that they allow for fast and efficient data retrieval, since data is organized in a predictable and structured way. 2. Easy to add/delete information: In this type of database, you can easily add or delete the information. 6  3. Predictable data structure: The hierarchical database model has a predictable and structured data structure, which makes it easier to understand and navigate. 4. Efficient storage of data: Since hierarchical databases store data in a parent- child relationship, they can be more efficient in terms of storage compared to other database models. 5. Good performance: Hierarchical databases can have good performance in terms of data retrieval and querying, especially for large datasets. Hierarchical Database Disadvantages 1. Limited flexibility: One of the major disadvantages of hierarchical databases is that they are not as flexible as other types of databases, and are not well suited for handling complex data relationships or changes in data structures. 2. Difficult to maintain and update: Hierarchical databases can be difficult to maintain and update, since changes to the data structure can impact the entire database. 3. Limited support for data manipulation: Hierarchical databases do not support complex data manipulation operations, such as data aggregation or data mining. Network Database Management system Data is stored in the network structure in the form of interconnected string of data, and thus this structure represents more complex logical relationships. Networked databases are still used with database management systems for large computer systems. This rule represents a pattern of many-to-many relationships between records, for example the relationships of multiple students in different courses, or multiple professors. In other words, the users can enter the data element by choosing One of several data access paths. Among its disadvantages is that it is inflexible, difficult, or complex in terms of programming and maintenance. However, it handles information efficiently. The following figure shows the network database. 7 Relational Database Management systems It is one of the most widely used and widespread types of rules, especially after the emergence of database management system packages with personal computer systems. The structure of the database consists of tables called relationships. Each table consists of columns representing fields and rows representing records. The table is linked through key fields (key field). The main and the secondary key field) It also enables us to easily integrate information from various sources, as it is more flexible than other types of databases, as shown in the figure, but the most important problems that this type faces is the weakness in processing efficiency, as the response time can be slow If there are a large number of requests to access the data that are selected, drawn and retrieved from the tables. 8 Types of relationships between tables in databases The table represents the basic unit in relational databases, and the relationship is the one that connects tables with each other through a common factor between these tables. There are many types of relationships between tables, which can be illustrated by the following example: There are several employees in a company, several departments, and it owns several projects, so how can the relationships between entities be represented? 1. A one-to-one relationship (1:1), which is represented in the following general form: E1 R E2 It is the linking of two tables so that one record in the first table corresponds to one record in the second table, for example, the citizen and his national number. The following figure represents an illustrative example of a one-to-one relationship between employees and the departments in which they work. 2. One-to-many or many-to-one relationship (1:M or M:1) as follows: E1 R E2 It is the joining of two tables so that one record in the first table corresponds to more than one record in the second table. For example, the student and the books he borrows from the library. 3. The many-to-many relationship (M:M), as follows: It is the association of two tables so that one record in both tables corresponds to more than one record in the second table. An example of this is the presence of several employees who share several books, professors, and students. 9  Keyboard shortcuts Ctrl + X Cut the selected item. Ctrl + C Copy the selected item.. Ctrl + V Paste the selected item. Ctrl + Z Undo an action. Ctrl + Y Back forward. Ctrl + W close the window in use Alt + Tab Switch between open applications. Alt + F4 Close the active item or exit the active application. Ctrl + P print the current page. Ctrl + mouse wheel key to zoom in and out of the current screen. F2 Rename the selected item. F3 Searches for a file or folder in File Explorer. F5 Refreshes the active window. F10 Activates the menu bar in the active application. Alt + Page Up Move up one screen.. Alt + Page Down Move down one screen.. Ctrl + A Select all items in a document or window. Ctrl + D or Delete Delete the selected item and move it to the Recycle Bin Ctrl + E Open Search (in most applications). Ctrl + R or F5 Refresh the active window. Ctrl + Right Arrow Move the cursor to the beginning of the next word. Ctrl + Left Arrow Move the cursor to the beginning of the previous word. Ctrl + Esc Open the Start menu. Ctrl + Shift + Esc Open the Task Manager. Shift + Delete Permanently delete the selected item without moving it to the Recycle Bin Esc End or exit the current task. Prt Sc to take a screenshot of the entire screen. 10