Network Working Group D.L. Mills Request for Comments: 996 University of Delaware February 1987
Network Working Group H. Clark Request For Comments: 1856 BBN Planet Category: Informational Septe
给定查询的不同执行策略可能会有不同的代价，构造具有最小查询执行代价的查询执行计划是数据库系统的职责。查询优化是为了查询选择最有效的查询策略的过程。查询优化是尽量找出与给定表达式等价的、但是执行效率更高
一、Update Statistics的作用 为了提高数据库的效率，INFORMIX提供了一个基于成本的查询优化器，
Network Working Group M. Lambert Request For Comments: 1857 Pittsburgh Supercomputing Center Obsol
Network Working Group B. Stockman Request for Comments: 1404 NORDUnet/SUNET January 1993 A Model
Network Working Group A. McKenzie RFC# 612 BBN-NET NIC # 21404 16 January 1974 Updates: RFC# 601
Network Working Group Edward Taft (PARC-MAXC) Request for Comments: 618 Feb 1974 NIC #21989 A Few
Network Working Group A. McKenzie Request for Comments: 566 BBN-NET NIC: 18801 4 September 1973 Up
Network Working Group A. McKenzie RFC# 601 BBN-NET NIC # 20905 14 December 1973 Updates: RFC# 586