5. Distributed Query Processing Chapter 7 Overview of Query Processing Chapter 8 Query Decomposition and Data Localization
1 5. Distributed Query Processing Chapter 7 Overview of Query Processing Chapter 8 Query Decomposition and Data Localization
Outline Overview of Query Processing(查询处理) Query Decomposition and Localization(查询分解 与定位)
2 Outline Overview of Query Processing (查询处理) Query Decomposition and Localization (查询分解 与定位)
Query Processing High level user query Quer Processor Low level data manipulation commands
3 Query Processing High level user query Low level data manipulation commands Query Processor
Query Processing Components Query language that is used SQL ( Structured Query Language) Query execution methodology the steps that the system goes through in executing high-level (declarative)user queries Query optimization How to determine the best execution plan?
4 Query Processing Components Query language that is used SQL (Structured Query Language) Query execution methodology The steps that the system goes through in executing high-level (declarative) user queries Query optimization How to determine the “best” execution plan?
Query language Tuple calculus:(t F(t) where t is a tuple variable, and f(t is a well formed formula Example Get the numbers and names of all managers tENo, ENAMeIt E EMP At(TITLE)="MANAGER")
5 Tuple calculus: { t | F(t) } where t is a tuple variable, and F(t) is a well formed formula Example: Get the numbers and names of all managers. t(ENO,ENAME)|t EMPt(TITLE) = "MANAGER" Query Language