1 / 21

Overview of Databases

Overview of Databases. Content. Databases Example: Access Structure Query language (SQL). What is a Database?. Database is an organized collection of related data, typically stored on disk, and accessible by possibly many concurrent users.

Download Presentation

Overview of Databases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Overview of Databases

  2. Content • Databases • Example: Access • Structure Query language (SQL)

  3. What is a Database? • Database is an organized collection of related data, typically stored on disk, and accessible by possibly many concurrent users. • Have programming capability to access and manipulate data • Three traditional types of database: • hierarchical • relational (most prevalent type) • network • New: object-oriented

  4. Database • Example databases: • Oracle • Sybase/Microsoft SQL • IBM’s DB2, IMS and SQL/DS • dBase • Access

  5. Database • Relational database: • It is a tabular database in which the data is defined so that it can reorganized and accessed in a number of different ways. • Tables are used to make it easy to maintain and data

  6. Database • Advantage of relational databases: • easy to create • easy to access • easy to extend • Possible disadvantage • Limited set of content (compared to object oriented databases).

  7. Database • Relational database structure: • set of tables containing data fitted into predefined categories; • each table (relation) contains one or more data categories in columns. • each row contains a unique instance of data for the categories defined by column.

  8. Programming • Database systems also have some programming capability • Often using SQL (see later) • Allows for accessing and manipulating data to form a report or to answer a query.

  9. Access • Relational database • Integrates data from spreadsheet and other database • User friendly • Easy to use (help wizard) • Limited in scale of application (small applications best)

  10. Features of Access • Database Wizard • Simple Query Wizard • Filter by selection • Integration with Form, filter by form • Report output

  11. Relationships in Access • Multiple tables in one database • Matching key fields between table • A key is usually a field with the same name in both tables. • Such key is primary key for one table, foreign key in the other table.

  12. Access : Database Note: tables, queries, forms and reports.

  13. Access: Table Table is where the data is kept

  14. Access: key Need to have a key to link data across tables

  15. Access: Macros and Modules • A macro is a set of one or more actions that each perform a particular operation, such as opening a form or printing a report. • Macros can help to automate common tasks. For example, a macro can run to prints a report when a user clicks a command button. Module • A module is a collection of Visual Basic for Applications declarations and procedures that are stored together as a unit.

  16. Access: Report Predefined report can be generated on demand from data.

  17. Database Programming • Access can use VBA or SQL for programming. • VBA not a standard. • SQL (see later) is used by most database systems.

  18. SQL • SQL: Structured Query Language • It is used to query from and update database. • Systems using SQL: • Oracle • Sybase • Microsoft SQL server • Access

  19. SQL • Standard SQL commands: • Select • Insert • Update • Delete • Create

  20. SQL Example

  21. SQL Example • To find out the ‘Category name’ when ‘Category ID’ equals to 1 SELECT Category name FROM Categories WHERE Category ID=1 Note: ‘Category name’ and ‘Category ID’ are column/field, ‘Categories’ is the table

More Related