Queries and related tables

A Microsoft Access query is a question about the information stored in Access tables. Your query can be a simple question about data in a single table, or it can be a more complex question about information stored in several tables. After run query, Microsoft Access returns only the information you requested.

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Tables are the main objects used in databases. (Without tables, and thus without data, you don’t have much of a database!) In Access 2010: Part I you learned that a table contains one or more records (or rows of data) and a record contains one or more fields. In this ebook you will go a step further and learn much more about the usage of tables, including how to build them from scratch. Further you will learn how to set field properties, create lookup fields and relate tables.

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In a normalized database, the data to be viewed can be stored in multiple tables. When you need to view data from related tables together, you can query the data by joining the tables with the help of common attributes. You can also use subqueries where the result of a query is used as an input for the condition of another query. This chapter discusses how to query data from multiple tables by applying various types of joins, such as an inner join, outer join, cross join, equi join, or self join. Further, it explains how to use subqueries....

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Chapter 33: Advanced Object-Oriented Concepts s s The object table itself is not mentioned in the query. The only table listed in the query is KEEPER. You do not need to know the name of the object table to DEREF its values. The entire referenced row object was returned, not just part of the row. 615 These are significant differences that separate object queries from relational queries. Thus, when querying your tables, you need to know the way in which their relationships are established.

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Early relational systems used indices as table replicas that allowed vertical partitioning, allowed associative search, and allowed con- venient data ordering. Database optimizers and executors use semi-join on these structures to run common queries on covering indices. These query strategies give huge speedups. These early ideas evolved to materialized views (often maintained by triggers) that went far beyond simple covering indices and provided fast access to star and snowflake schema. In...

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As an example of how queries are executed, consider the query shown in Figure 5. In Figure 6, the processes used to execute the query are shown along with the flow of data between the various processes for a Gamma configuration consisting of two processors with disks and two processors without disks. Since the two input rela- tions A and B are partitioned across the disks attached to processors P1 and P2, selection and scan operators are ini- tiated on both processors P1 and P2.

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After completing this unit, you should be able to: List the characteristics of an XML document that help determine the right type of database, define and describe content management databases, compare relational database structures to XML document structures, list the limitations of relational data tables with structured data, define and describe what Object-Oriented databases provide, describe the status of XML-based queries.

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Language Integrated Query (LINQ), as well as the C# 3.0 and VB 9.0 language extensions to support it, is the most import single new feature of Visual Studio 2008 and the .NET Framework 3.x. LINQ is Microsoft ’ s first attempt to define a universal query language for a diverse set of in - memory collections of generic objects, entities persisted in relational database tables, and element and attributes of XML documents or fragments, as well as a wide variety of other data types, such as RSS and Atom syndication feeds. Microsoft invested millions of dollars in Anders Hejlsberg...

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Part III Beyond Relational creating tables with XML columns, and allows declaring XML variables and using them as parameters and return values. XQuery is a W3C-recommended language created to query and format XML documents. XQuery can be used to query XML documents just like a SQL query is used to retrieve information from relational tables. The XML data type implements a limited subset of the XQuery specification and a T-SQL query can use XQuery to retrieve information from XML columns or variables.

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This course offers students an introduction to Oracle Database 10g database technology. In this class, students learn the concepts of relational databases and the powerful SQL programming language. This course provides the essential SQL skills that allow developers to write queries against single and multiple tables, manipulate data in tables, create database objects, and query meta data.

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At present, adapting an Information Extraction system to new topics is an expensive and slow process, requiring some knowledge engineering for each new topic. We propose a new paradigm of Information Extraction which operates 'on demand' in response to a user's query. On-demand Information Extraction (ODIE) aims to completely eliminate the customization effort. Given a user’s query, the system will automatically create patterns to extract salient relations in the text of the topic, and build tables from the extracted information using paraphrase discovery technology. ...

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Chapter 8 describes more advanced features of the SQL language standard for relational databases. In this chapter present more complex features of SQL retrieval queries, such as nested queries, joined tables, outer joins, aggregate functions, and grouping.

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Chapter 8 describes more advanced features of the SQL language standard for relational databases. In this chapter present more complex features of SQL retrieval queries, such as nested queries, joined tables, outer joins, aggregate functions, and grouping. Inviting you to refer for more information.

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In this lesson, you will learn to: Identify the following kinds of relations: Base tables Query results Views Create tables Alter tables Remove tables Query tables and work on them Define views Perform DML operations on views Identify the different types of views Identify data integrity constraints.

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The relational database uses the concept of linked two-dimensional tables consisting of rows and columns, as shown in Figure 1-2. Unlike the hierarchical approach, no predetermined relationship exists between distinct tables. This means that the data needed to link together the different areas of the network or hierarchical model need not be defined. Because relational users don’t need to understand the representation of data in storage to retrieve it (many such users created ad hoc queries against the data), ease of use helped popularize the relational model....

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At the end of this course, you should be able to
Describe the relational database approach, concepts, terminology, and operators.
Create database structures such as tables and views using Structured Query Language (SQL).
Store, retrieve, and update data in the database.
Develop PL/SQL blocks of application code using Procedure Builder to manipulate data.

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