Concept - Relational Database
A database is a structured collection of data for one or more applications, with the relationships between data items; a query language gives a uniform interface (s.2). A relational database is built from tables of rows and columns; each column holds one type of data; ideally one column has all-unique values forming the row’s key; tables are linked by a unique identifier present in all tables (s.4-5).
| Term | Synonyms / meaning (s.7) |
|---|---|
| Relation | table, file |
| Tuple | row, record |
| Attribute | column, field |
| Primary key | uniquely identifies a row |
| Foreign key | links one table to attributes in another |
| View (virtual table) | result of a query returning selected rows and columns from one or more tables |
Example (s.9): Department(Did PK, Dname, Dacctno) and Employee(Ename, Did FK, SalaryCode, Eid PK, Ephone); the view joins them to show Dname, Ename, Eid, Ephone for each of the 7 employees. Two employees are called Robin (Eid 2345 and 2976), so only Eid identifies a row.
Related: Concept - SQL, Concept - Database Access Control Policies. Appears in 05 Database Security - Chunk 01 (s.1-38).