| 浅析SQL中WHERE EXISTS子查询 |
| |
| 引用本文： | 袁红娟.浅析SQL中WHERE EXISTS子查询[J].长春师范学院学报,2006(6). |
| |
| 作者姓名： | 袁红娟 |
| |
| 作者单位： | 泰州师范高等专科学校 江苏泰州225300 |
| |
| 摘 要： | 结构化查询语言SQL是一个综合的、通用的、功能极强的关系数据库语言,而SQL语言的核心又是SELECT语句。其中WHERE子句的条件表达式表现得灵活而复杂,与谓词EXISTS所形成的嵌套查询也成为部分人理解的难点,本文将重点剖析WHERE EXISTS子查询的语法、执行流程及使用离散数学知识辅助解决复杂查询的实现方法。
|
| 关 键 词： | 数据库 SQL EXISTS 存在量词 全称量词 子查询 |
Analysis on the Subquery about WHERE EXISTS during SQL |
| |
| YUAN Hong-juan.Analysis on the Subquery about WHERE EXISTS during SQL[J].Journal of Changchun Teachers College,2006(6). |
| |
| Authors: | YUAN Hong-juan |
| |
| Abstract: | The Structured Query Language(SQL) is a comprehensive and universal Relational Database Language which has strong functions,while the nucleus of the SQL is SELECT sentence.Among them the conditional expressions of WHERE clause is flexible and complicated,which form the nested query with EXISTS.Some people have difficulty in understanding this point.This article will emphasize on analyzing the grammar of WHERE EXISTS,executive flow and how to solve the complicated query by the assisting way of discrete mathematics. |
| |
| Keywords: | database SQL EXISTS existential quantifier universal quantifier subquery |
| 本文献已被 CNKI 等数据库收录！ |
