Port Said International Schools – National Section Revision Handout Better education for future generations Grade: 11 Define the following concepts:1. Data: the primary raw material of the information. 2. Information: it's the output of data processing. 3. The table: the vessel that contains a set of data for a certain topic where data are stored with the aim of retrieving them when needed. 4. Record: it's the place (Row) where we store different kinds of data for the same item. 5. Column: it's the place where we store one kind of data for many items. 6. Database: group of organized data inside a table or tables with the aim of retrieving them to make the required decisions. 7. Key attribute (Entity Key) (Primary Key): it's the attribute whose value can never be repeated inside the entity (unique). 8. Composite Key: it's more than a field in a table whose components together don't repeated, while each component can be repeated alone. 9. Foreign Key: it's a strange field in a table linked to a primary key in another table. 10. (One to Many) relationship: it's the ability for a record in the first table (One) to be linked to more than a record in the second table (Many), and any record from the second table (Many) can be linked to only one record in the 1 M Entity B first (One ). Entity A 11. (Many to Many) Relationship: it's the ability for a record from the first table to be linked to more than a record in the second table, and any record from the second table can be linked to more than a record in the first table. M N Entity B Entity A 12. (One to One) Relationship: it's the ability for a record from the first table to be linked to a single record in the second table, and any record from the second table can be linked to a single record from the first table. Entity A 1 1 Entity B 13. Intermediary (junk) table: is a table used to link between two tables, the relationship between them is (Many to Many). The fields of this table are the primary keys for the two tables and any relationship attributes. 14. Multi-Valued Attribute: is the attribute for an entity that can include more than one value. Example: when an employee has more than one qualification (bachelor + master degree … etc) 15. The Derived Attribute: is the attribute that can be deduced from another attribute. Example: when we want to calculate the age from the birthdate. Port Said International Schools – National Section Revision Handout Better education for future generations Grade: 11 16. Enforce Referential Integrity: it’s a system Microsoft Access uses to ensure that the user won’t accidently delete or change the related data. 17. Cascade Update Related Fields: used to automatically update the value of the related fields in the related table whenever any record is changed in the primary table. 18. Cascade Deleted Related Fields: used to automatically delete the value of the related fields in the related table whenever any record is deleted in the primary table. Relational Database Management System (RDBMS)'s advantages: 1. Designing the Relational Database Model (RDM) in an easy and interesting way for the user. 2. The ability to control the user inputs to reduce the chances of the entry errors. 3. The ability to make a calculated field in a form. Ex. Calculate a user's age after we put the birthdate. 4. Controlling the way of displaying data, using queries and reports. 5. Dealing with more than a table at a time. 6. The ability to create customized user interface for entering data (Form). Data types in Microsoft Access 1. Text: combination of letters and numbers that don't require calculations such as phone numbers, postal codes. The size is up to 255 characters. 2. Memo: like text type but it's longer, up to 65536 characters, and used for books and descriptions. 3. Number: used for numbers that will be calculated, and it has two types: a. Whole numbers: such as byte, integer, and long integer. b. Decimal Numbers: such as Single, Double, and Decimal. 4. Date/Time: used with dates and times. 5. Currency: used for money. This type prevents rounding off calculation results. 6. Yes/No: used for data that can be only one of two possible values such as Male/Female, On/Off. 7. Auto Number: usually used for primary key field and it's automatically incremented by 1 when a new record is added. 8. OLE Object: used for objects such as Word documents, pictures, Excel spreadsheets, and sounds. 9. Hyperlink: used for hyperlinks. The size is up to 64000 characters. Port Said International Schools – National Section Revision Handout Better education for future generations Grade: 11 Note: the data type of the primary key must be the same data type of the foreign key. Note: The (Many to Many) relationship can't be solved in Access and we must create an intermediary (junk) table. The Advantages of Database: 1. Store, classify, and organize data. 2. Easy to modify data at any time. 3. Easy to create forms to make data entry easier. 4. Using search and query are easier to find the stored data. 5. Displaying data and information using reports. Types of database in terms of Design View: 1. Hierarchical Database Model. 2. Network Database Model. 3. Relational Database Model. Advantages of Relational Database Model: 1. No repeating for data in more than a table. 2. Data integration. 3. Faster in processing and getting data from more than a table. 4. Low storage space of database. Example: you are required to create a database for a company and you will make the Entity Relationship Diagram (ERD) according to these requirements. 1. The company is divided into departzments, each one has a unique number and a name. 2. The department may have more than one location. 3. We must keep the employee data that include a non-recurred number, his name, gender, address, telephone and his salary. 4. The employee has to work in only one department and it’s important to know the number of the employees in each department. 5. There’s special employee for each department to run, and it’s important to know the starting date to run this department 6. The employee should work in a single project at least which has a unique number, name and a location. 7. It’s important to know the number of the weekly hours that each employee spends in each project. Port Said International Schools – National Section Revision Handout Grade: 11 Better education for future generations Entity Attributes Entity Key Employee Name – Gender - Address Telephone – Salary - EmployeeID. EmployeeID. Department DepartmentID – Location Name – NoOfEmployees DepartmentID Project ProjectID – Name - Location ProjectID First Entity Other Entity Employee Department Employee Employee Relationship Name Relationship Type Relationship Attributes Total Participation Work in department One to Many None Department - Employee Department Manage One to One Starting Date Department Project Work in Project Many to Many Number of Hours Employee Project Birthdate Gender Name Address Employee Salary M N 1 Work in Project NoOfHours EmployeeID Work in Department Manage 1 N 1 StartingDay Project Department Name Location ProjectID Name DepartmentID Location NoOfEmployees Very important Notes about the previous example: 1. Location attribute is a multi-valued attribute and it’s presented by double outline border. 2. NoOfEmployee attribute is a derived attribute and it’s presented by dotted line. 3. StartingDay and NoOfHours are shared attributes, that’s why they are connected to the relationship name.