CS 150 study guide1

CS 150 study guide1 - 1. DB Concepts Query- Question you...

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1. DB Concepts Query- Question you ask about data stored in a database. To answer, Access displays specific records and fields that answer your question. Table- A collection of fields that describe a person, place, object, event or idea. 2 dimensional, made up of rows and columns of data in a relational database. Each row and column is unique, and row and column order is unimportant. All entries are single-valued, each row describes a single entity. Database- A collection of related tables all stored in the same file. Relationship- joining 2 or more tables through a common field. primary key- A field, or collection of fields whose values uniquely and minimally identify each record in a database table and whose values do not change. nonkey field- A field that is not part of the primary key foreign key- A primary key field in one table that you use as a field in a second table to form a relationship between the two tables. data redundancy – A condition that occurs when you store the same data in more than one place; it wastes storage and can cause inconsistencies. redundant field- a field whose value is typed into more than one table. data inconsistency- when a redundant field has conflicting data in the different tables they exist entity integrity- when access forces you to type in a value in a primary key field null value- value that results from failing to enter a value into a field- not allowed for a primary key Data type- Field property that determines what field values you can enter for the field and what other properties the field will have. field property- characteristics of each field field size- how many characters are allowed to be stored for each field value 2. Query Functions of query (what can a query do?) Displays selected fields and records from a table Sorts records Performs Calculations Generates data for forms, reports and other queries
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This note was uploaded on 04/07/2008 for the course CS 150 taught by Professor Xu during the Spring '08 term at Bentley.

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CS 150 study guide1 - 1. DB Concepts Query- Question you...

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