Database purpose: is to organise and keep track of things, involving more than a single theme. Spreadsheets: Keep lists of single concept. Databases: Keep lists that involve multiple themes/concepts.
Database: A self-describing collection of integrated records.
Hierarchy of data elements: Bytes/data are grouped into columns/fields that are grouped into rows/records that are grouped into tables/files. Where, collection of tables + rows (also, ‘metadata‘) describes structure of database. Characters/bytes are the values or info.
Rows: key (column/s identifying unique row, found in every table), foreign keys (fields other than key, used to connect to table where field is primary key), and relational databases (uses tables, keys, and foreign keys).
Database self-describing: Contains descriptions of data, e.g. Field properties in Word
Metadata: Data that describe data, databases more useful/easier to use. E.g. field name/properties, data type, or description.
Components of database application system: User who uses database application (consisting of forms, reports, ect. app programs), database management system (processes data), database contains tables, relationships, and metadata.
Database application system: makes data from database more accessible/useful.
DBMS: a program used to create, process and administer a database. Usually licensed from vendors, products include Microsoft Access, Oracle, MySQL, DB2.
DBMS different from a database: A DBMS is a software program, while database is a collection of tables, relationships and metadata.
DBMS helps administer a database: Administrative functions (Security: accounts, passwords, ect.) Permissions: data access right for specific user/s (backup data, structure for performance, and remove unwanted data).
Database applications improve databases: by a collection of forms (used to read, insert, modify, delete data), reports (show data structured/computed), queries (means to derive answers from data), and multiple application programs (with multiple users) can process database.
Users > Database Applications (e.g. stock management app or purchasing app) > DBMS > Inventory Database
Enterprise DBMS: Processes large organisational/workgroup databases and supports many users.
Personal DBMS: Designed for smaller, simpler database applications and supports fewer than 100 users.
Multi-User Processing Considerations: Users can work with same enterprise database and records concurrently. Lost-update problem: an update to a record is lost, from a transaction in an application due to an update made by another transaction at the same time. Locking: Used to ensure a transaction does not interfere with other transactions, coordinates activities between unrelated users.
Database application systems require development: First, developers interview users to identify/develop requirements for applications. Second, analyse existing forms, reports, queries and other user activities. Third, sum requirements/themes in data model. Fourth, users review/validate data model. Finally, after users approve data model, build database.
Normalisation: Converting natural description of data in the data model to structured tables (data about single theme/entity) for use in relational database. To minimise duplication of data and avoid data integrity problems.
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