Object-oriented DBMS requirements

The requirements on an object-oriented DBMS for management of information in a large, complex enterprise are presented. These requirements aid in the achievement of an environment characterized by data sharing, open architectures, application and data portability, and assurance of data integrity. They were defined from the point of view of a user of the DBMS; therefore they describe the expected functionality of the DBMS and do not specify the method of implementation to achieve this functionality. They encompass requirements on the data model, query and data manipulation languages, the system architecure, interfaces to the system, change management, and transaction management.     

SQL性能优化——表连接的分析

介绍两个表连接的几种常用方式和不同方式的内部机制.在比较3种不同表连接方式的优缺点基础上,选择一种好的方式来优化表连接,以提高查询速度,并结合中国邮政报刊发行系统数据库开发中遇到的生产实际,分析3种表连接方式的优劣.     

SQL语言中量词和空值的使用技术

在ＳＱＬ语言中可以引入全称量词符号ＦＯＲＡＬＬ，使ＳＱＬ语言使用更为自然，方便。本文讨论全称量词，存在量词和ＡＬＬ三种谓词之间的转换，联系和区别，以及空值存在时ＳＱＬ的使用技术。     

研究生信息管理系统的设计与实现

基于实践对研究生信息管理系统进行了设计与实践,方便了教师和学生,提高了工作效率。     

SQL查询中外联结的使用

SQL语言是数据库应用中的一种查询语言,在多库查询中,经常用到联结的操作,本文讨论了SQL语言中外联结的使用,并给出了几个具体的例子.     

Logical errors in database SQL retrieval queries

SQL is often used to express questions imposed by users. It is well known that this process is not error-free in that it may result in syntactically or semantically incorrect SQL queries. This article is meant to probe deeper into SQL queries that are incorrect, due to delusion errors. A classification of natural language questions will be introduced. The purpose of this classification is two-fold. Firstly, it gives insight into possible errors and enables us to distinguish between types of errors. Secondly, it is a means of determining the influence of measures (for instance, SQL training) that can be taken to reduce the number of aforementioned errors. For discussion, several of these measures will be presented and related to the classification.Abbreviations RA Relational algebra - SQL structured query language     

SQL extension for spatio-temporal data

An SQL extension is formalized for the management of spatio-temporal data, i.e. of spatial data that evolves with respect to time. The extension is dedicated to applications such as topography, cartography, and cadastral systems, hence it considers discrete changes both in space and in time. It is based on the rigid formalization of data types and of SQL constructs. Data types are defined in terms of time and spatial quanta. The SQL constructs are defined in terms of a kernel of few relational algebra operations, composed of the well-known operations of the 1NF model and of two more, Unfold and Fold. In conjunction with previous work, it enables the uniform management of 1NF structures that may contain not only spatio-temporal but also either purely temporal or purely spatial or conventional data. The syntax and semantics of the extension is fully consistent with the {SQL:2003} standard.     

J2EE项目中数据访问策略的选择

本文介绍了目前J2EE项目数据访问策略的选择，其中重点描述了O／R映射这种数据访问策略的特点及其适用的最佳条件，它可以帮助我们在项目的开发阶段通过清晰的映射方案构造出高效率的DAO层，为项目的成功打下良好的基础，特别是对于项目的式样变更以及后期维护．这种数据访问策略提供了最大程度上的灵活性。     

基于SQL Server的OLAM的研究及应用

OLAM(On-line Analytical Mining)是当前的热点技术,是融合了联机分析处理(OLAP)和数据挖掘(Data Mining)的一种新的数据挖掘技术。本文主要研究数据仓库中OLAP,On-line Analytical Processing和数据挖掘技术,这两个技术是商业智能中的核心技术和主要内容,在两者的基础上引入OLAM的概念,并阐述其基本原理和核心技术。基于微软的SQL Server平台,为一个商业案例建立数据仓库,利用Analysis Services服务,建立销售分析的多维数据集,利用OLAM的基本模型实现OLAP和聚类挖掘技术的结合,借助两者的各自优势,得到很好的客户聚类分析结果。