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Specific Objectives Content1. explain the concept of a database; Definition of database: repository of information; collection of tables that are related to each other. 2. use terminology commonly associated with a database: Database terminology: table (relation), entity, tuple, attribute, primary key, secondary key, composite key, candidate key, alternate key, foreign key. 3. distinguish among terminology associated with files and databases: Row (tuple, record), column (attribute, field), key. Data types: alphanumeric; numeric; data; logical. 4. outline the advantages and limitations of databases: Comparison with files with regards to: Speed; Ad hoc queries; standardization; present multiple views of the same data. 5. create a database: Table structure with at least three data types and populate with at least twenty-five records. Use of wizard is prohibited. 6. modify a table structure: Adding new fields, deleting fields, changing field definitions. 7. sort a database: Arranging data in numeric, alphabetic; or alphanumeric format. Report generating facilities of the database package, including use of sorting, grouping statistical and summary features, for example, count, sum and average. 8. establish relationships: Use of joins, merge tables/files. 9. query a database using multiple search conditions: Using more than one criterion; use of select, calculated fields. 10. determine the results of a search on a database given multiple conditions: Two or more fields involving the use of relational and logical operators. 11. generate reports to the screen, printer and files: Report generating facilities of the database package, including use of sorting, grouping, statistical and summary features, for example, count, sum and average.
A database is a structured collection of interrelated data. In a relational database, data is stored in tables. The difference between the terms “data” and “information”: A piece of Data is a fact that can be represented as audio, video, text or number(s). By itself, it may not be relevant, but if it is processed and put in a certain context, it takes on meaning and becomes information. Information is the context, the meaning attached to the data. For an example, the sound for alarm is data. If you listened to it out of context, it would be just an unpleasant and penetrating sound. After it was assigned to the meaning "imminent danger", it became (well known) information.
Examples of large database use: plane ticket reservations governmental institutions databases bank accounts patient data
1.1 Database organization What database tables contain and what table data apply to? A Table is the most important database element. It is composed of rows and columns that contain information on a certain subject. For example, the table "Customers" contains the necessary information about customers. A Record in a table is displayed as a line and contains information about a subject, e.g. relevant information about a customer. Fieldsare individual record characteristics which are in columns within a table. The type of data that can be entered in a field is specified as the data type (textual, logical, currency,numeric etc.), e.g. name, address, city, telephone, e-mail etc. Besides the type, within the fields we can also determine: Field size Format – e.g. we can specify what currency indicator is added to the amount Default Value – if nothing is entered, the value that we enter here will be written in the field Validation Rule – checks whether the entered information is correct, i.e. checks whether the set criteria is met
Why should each table field contain only one data element, one type of information? In Figure 1, Table records and fields, you can see an example of good table design, i.e. each field contains only one data element. Name is entered in one field, last name in another, street and number (address) in the third etc. A bad design example would be this:
the previous example, there are two data elements in one field (first and last name in the Name field) and three data elements in another (street number, city and zip code). The data is inflexible, making it very difficult to sort and create queries and reports. Better design example in comparison to the previous table would be this: Figure 1
With every data element in a separate field, it is easier to sort and create queries and reports. Connection between data types and field content Field content is a particular data type within a table. It can be text, number, currency, date and time, yes / no, etc. To add a field, click the right mouse button on the table header labeled Click to Add. Another way to add a field is via the Design View, in the Data Typecolumn. To add a field, click the right mouse button on the table header labeled Click to Add. Another way to add a field is via the Design View, in the Data Typecolumn.
Basic field propertiesTable fields have the appropriate properties, such as field size, formatting and default values. These properties can be changed in the Field Properties.
Field Size– for example, pre-set to 255 text characters. Default Value– for example, for Yes/No data type, default value is 0.
Date: 2015-12-17; view: 1554
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