WHERE EXISTS子查询应用研究  

Research of The WHERE EXISTS Query Application

作　　者：张艳霞[1] 陈丹琪[1] 韩莹[1] ZHANG Yan-xia,CHEN Dan-qi,HAN Ying（Disaster Information Engineering Department,Institute of Disaster Prevention,Beijing 101601,China）

机构地区：[1]防灾科技学院灾害信息工程系,北京101601

出　　处：《电脑知识与技术》2012年第5期2985-2987,共3页Computer Knowledge and Technology

摘　　要：SELECT语句作为SOL语言的核心,可以通过使用WHERE子句实现灵活而复杂的查询操作。其中,与谓词EXISTS所形成的嵌套查询是理解的难点,该文将通过分析查询实例,探讨如何使用WHERE EXISTS子查询实现复杂的查询操作。The SELECT statement as part of the SOL language core,can be achieved by using the WHERE clause to realize flexible and complex query operation.Among them,and predicate EXISTS formed by nested query is the difficulties to understand,this paper through the analysis of query examples,discusses how to use the WHERE EXISTS query to achieve complex query operation.

关 键 词：数据库 SOL EXISTS 子查询 

分 类 号：TP311[自动化与计算机技术—计算机软件与理论;自动化与计算机技术—计算机科学与技术]