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在数据库系统中,数据查询是一种实际应用.本文主要讨论Visual FoxPro数据库当中与查询密切相关的索引方法.数据库中提供顺序查询和索引查询两种查询数据的方法,以及VIEW(数据工作期)窗口和RQBE(范例关系查询)窗口两种交互式查询工具. 相似文献
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对象关系数据库系统PostgreSQL提供的索引类型有:B-tree,R-tree,GiST和Hash。每种索引提供了适合不同查询类型的最优算法,而其中在大多数情况下都能适用,尤其适用于已经排好序的数据上的等值查询和范围查询。本文以最常用的B树索引为例,对PostgreSQL系统索引机制的建立进行了分析和探讨。 相似文献
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随着数据库技术的广泛应用,数据库中存储的数据日积月累不断的增加,数据库查询的效率不可避免的降低,如何提高数据库的查询效率成为每个数据库管理员必须研究的问题。首先介绍了数据库索引的概念和作用,解析了两种不同索引结构的区别,再通过实例分析,介绍如何建立合理的数据库索引来优化数据库查询。 相似文献
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二级索引方案是分布式存储研究的重要分支之一,基于通用目标设计二级索引方案可避免单一业务编程繁琐问题,使实施人员更多地关注业务本身而非编程细节。以HBase数据库为研究对象,引入分布式索引机制,通过重写观察者Observer协处理器方法,操作完数据后立即触发创建或更新索引的请求,进一步在SolrCloud中完成对索引的管理。反向进行多条件组合查询时,先在SolrCloud中查询包含行键和索引列的文档,再以行键为条件查询并获取HBase记录。部署通用方案,实验证明该方案很好地满足了创建和维护HBase二级索引的要求,且保证了索引与记录的一致性,对进一步研究分布式存储二级索引方案有一定的指导意义。 相似文献
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与标准的方法XQuery查询语言不同,XML文档的关键字查询能使用户方便地访问XML数据,不必考虑数据复杂模式和掌握复杂查询描述语言。文章对关键字查询中索引技术进行研究,提出了一种基于Dewey编码的查询索引进行解决,以综合分析XML数据的值信息和结构信息,达到子树返回和路径返回的精确查询的目标。 相似文献
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对当前的XML索引需要改进的地方进行分析,给出了一个较通用的索引机制。首先提出一种XML文档编码规则,在此基础上设计支持路径查询和信息检索的索引结构,并给出了对文档重复元素和文本节点索引词汇进行归并处理的索引算法。索引算法只需对文档遍历一次,所得到的索引文件占用空间也比GUID和倒排文档少,并且利用这些索引文件能实现任意粒度、任意形式的内容、结构和属性查询。 相似文献
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蔡才俊 《河北师范大学学报(哲学社会科学版)》1989,(1)
一问题的提出我们通常使用的地名索引大概可分三类:一是经纬法;二是分段纵横交叉法;三是经纬分段纵横交叉并用法.《中华人民共和国地图》地名索引就是经纬法的实际例子.《中华人民共和国分省地图集》(汉语拼音版)地名索引属于分段交叉法.《The Times Atlas of the 相似文献
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Catherine M. Sleezer James Gregson Robert Nolan William Venable Melvin Miller 《Performance Improvement Quarterly》1998,11(4):76-90
The many changes in today's workplace argue for equivalent changes in educating human resource development (HRD) professionals. The need for HRD curricular changes to be thought out fully and future-focused warrants the use of systematic methods for formulating, solving, and learning more about how to formulate and solve curriculum problems. Deliberative inquiry is such a method. This research methodology is directed toward curricular decision-making as it occurs within a specific context and, simultaneously, toward learning how to formulate and solve such problems. This study focuses on how faculty members in one university department used the problem formulation phase of deliberative inquiry to assess future needs for their HRD specialization. The article first overviews the research methodology of deliberative inquiry and then describes the systematic approach-subject matter analysis-that was used to structure the problem formulation relative to HRD curricular needs. The problem formulation process clarified stakeholders' values. It also resulted in reframing the situation, which led to new insights about the issues facing the HRD curriculum and ways to address them. 相似文献
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Florence Le Hebel Andrée Tiberghien Pascale Montpied Valérie Fontanieu 《International Journal of Science Education》2019,41(11):1517-1540
This study focuses on the teachers’ predictions of the students’ performances – in particular the middle-low achievers – while solving tasks testing inquiry competencies. The tasks come from PISA science. More specifically we study science teachers’ predictions for several aspects: levels of difficulty of the tasks, the potential sources of difficulty and the potential difficulty in solving it for medium-low achievers. We also study what assessed competencies are identified by science teachers in the tasks. Our approach is a questionnaire-based study. A sample of French teachers in science and technology (125) responded to the questionnaire. The teachers show a rather good ability to predict inquiry task levels of difficulty for medium-low achievers and are able to identify relevant potential sources of difficulty or easiness in the items. However, they are not aware of some essential difficulties that medium-low students encounter while solving science inquiry tasks. Moreover, the teachers have difficulty identifying the competencies that are tested by an item. 相似文献
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李庆福 《河北北方学院学报(社会科学版)》1998,(Z2)
通过分析Windows环境中生成的位图文件的存储结构,以及显示位图的基本原理,给出了在DOS环境中使用位图的基本方法。最后,给出了可以直接在DOS中编译执行的、用于显示位图的C语言源程序。 相似文献
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无缝连接图是经过无缝化处理的位图图块,是一种非常特殊的位图.利用Flash AS3的位图处理代码,分析用代码生成无缝连接图的方法,设计了一个动态无缝连接图的实例,并且提供了将外部＂照片＂位图嵌入到无缝连接图中的方法,为无缝连接图的主题图案设计提供了方便、灵活的设计思路与方法. 相似文献
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主要研究了操作系统中利用位示图进行存储分配和回收的基本理论。详细介绍了用位示图实现存储资源分配的算法流程和二级位示图目录的有关概念,并推广到多级位示图目录法。对位示图分配方式的管理开销进行了分析与探讨。 相似文献
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The concept of social presence proposed in studies on communities of inquiry has highlighted both the importance and the challenges of integrating aspects such as affective and relational expressions among team members while solving collaborative learning tasks, in order to advance in a global comprehension of learning processes. This paper presents a theoretical and methodological proposal for tackling this issue from a socio-cultural perspective by analysing the participants’ discourse in relation to expressions of self-competence (at an individual and group level) concerning the task and group cohesion (task cohesion and social cohesion). This proposal’s potential is illustrated by the empirical results of a case study that analyses social presence during a collaborative work task by university students using the Moodle learning platform. 相似文献
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探究式学习往往是一个问题解决的过程。本文围绕着问题解决学习所需的支撑性要素,从活动理论和情境认知学习理论的视角分别对问题、相关案例、认知工具、学习共同体和资源几方面进行了论述,由此提出了一个信息技术支持下的探究式学习环境设计的基本构架。 相似文献
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展示"算术平均数与几何平均数"一节中例1及其应用的教学片段,暴露学生在解决同一问题中的认知冲突和思维的差异性、多维性,经历"生疑——解惑——明理"三个阶段,揭示学生在知识建构中经历探究过程的意义及重要性。尝试将数学学习过程成为在教师引导下的"再创造"过程,使学生形成积极主动、勇于探索的数学学习方式。 相似文献
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Science as inquiry and mathematics as problem solving are conjoined fraternal twins attached by their similarities but with distinct differences. Inquiry and problem solving are promoted in contemporary science and mathematics education reforms as a critical attribute of the nature of disciplines, teaching methods, and learning outcomes involving understandings, attitudes, and processes. The investigative and quantitative processes involved in scientific inquiry include seeking problems, identifying researchable questions, proposing hypotheses, designing fair tests, collecting and interpreting data as evidence for claims, constructing evidence-based arguments, and communicating knowledge claims. Within this empirical context, science and mathematics come together to solve problems with evidence, construct knowledge claims, communicate claims, and persuade others that the claims are valid and useful. This study examined the intersection of inquiry and problem solving and the use of mathematics in 26 extracurricular open science inquiries. The category and the appropriateness of the mathematical procedures revealed these students used measurement, numeracy skills of counting and calculation, and tables and graphs in their science inquiries. It was found that most measurements in the science inquiries were used appropriately, but there is room for improvement with other mathematical procedures that involve higher-level thinking skills, such as analyzing and calculating numerical data and interpreting graphs and tables. The findings imply that mathematics and science are connected in inquiry and should be extended to solve real-life problems and that instruction should emphasize comprehending and interpreting data. 相似文献