Chapter 25 - Advanced data types and new applications. This chapter covers advanced data types and new applications, including temporal datababases, spatial and geographic databases, multimedia databases, and mobility and personal databases. This chapter is suited as a means to lay the groundwork for an advanced course. Some of the material, such as temporal and spatial data types, may be suitable for self-study in a first course. | Chapter 25: Advanced Data Types and New Applications Database System Concepts, 6th Ed. ©Silberschatz, Korth and Sudarshan See for conditions on re-use Chapter 25: Advanced Data Types and New Applications Temporal Data Spatial and Geographic Databases Multimedia Databases Mobility and Personal Databases Database System Concepts - 6th Edition ©Silberschatz, Korth and Sudarshan Time In Databases While most databases tend to model reality at a point in time (at the “current” time), temporal databases model the states of the real world across time. Facts in temporal relations have associated times when they are valid, which can be represented as a union of intervals. The transaction time for a fact is the time interval during which the fact is current within the database system. In a temporal relation, each tuple has an associated time when it is true; the time may be either valid time or transaction time. A bi-temporal relation stores both valid and transaction time. Database System Concepts - 6th Edition ©Silberschatz, Korth and Sudarshan Time In Databases (Cont.) Example of a temporal relation: Temporal query languages have been proposed to simplify modeling of time as well as time related queries. Database System Concepts - 6th Edition ©Silberschatz, Korth and Sudarshan Time Specification in SQL-92 date: four digits for the year (1--9999), two digits for the month (1--12), and two digits for the date (1--31). time: two digits for the hour, two digits for the minute, and two digits for the second, plus optional fractional digits. timestamp: the fields of date and time, with six fractional digits for the seconds field. Times are specified in the Universal Coordinated Time, abbreviated UTC (from the French); supports time with time zone. interval: refers to a period of time (., 2 days and 5 hours), without specifying a particular time when this period starts; could .
