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PRTV (''Peterlee Relational Test Vehicle'') was the world's first relational database management system that could handle significant data volumes. It was a relational query system with powerful query facilities, but very limited update facility and no simultaneous multiuser facility. PRTV was a follow-on from the very first relational implementation, IS1. == Features == PRTV included several firsts in the relational database area: * implemented relational optimizer * implemented cost based relational optimizer * handle tables of 1000 rows up to 10,000,000 rows * user defined functions (UDFs) within an RDB (also a large suite of built-in functions such as trigonometric and statistical) * geographic information system based on an RDB (using UDFs such as point-in-polygon). PRTV was based on a relational algebra, Information Systems Base Language (ISBL) and followed the relational model very strictly. Even features such as user defined functions were formalized within that model. The PRTV team also introduced surrogates to the relational model〔 to help formalize relational update operations; and a formalisation for updating through views. However neither of these was implemented within PRTV. PRTV emphatically did ''not'' implement NULL values, because this conception was introduced only in 1979. PRTV was itself never available as a product, but the Urban Management System built on it was available as a limited IBM product. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IBM Peterlee Relational Test Vehicle (PRTV)」の詳細全文を読む スポンサード リンク
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