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Problems using spreadsheets

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-Redundancy -Difficulty accessing the related data -Limited Security -Size Limitation

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Redundancy

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Duplication of data or the storing of the same data in more than one place

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Database

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Structure that can store information about different categories of information and relationships between those categories of information.

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Entity

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Person, place, object, event, or idea

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Attribute

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Characteristic or property of an entity. May also be called a field or column

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Relationship

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Association between entities

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Data File

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File used to store data. Computer counterpart to ordinary paper file.

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Entity-Relationship(E-R) diagram

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Visual way to represent a database. Rectangles represent entities. Lines represent relationships between connected entities

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Database Management System(DBMS)

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Program, or collection of programs, through which users interact with a database.(Access, Oracle, DB2, MySQL, and SQL Server)

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Database design

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Determining the structure of the required database.

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Advantages of Database Processing

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- Getting more information from the same amount of data - Sharing Data - Balancing conflicting requirements - Controlling redundancy - Facilitating consistency - Improving integrity - Expanding Security - Increasing Productivity - Providing Data Independence

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Disadvantages of Database Processing

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- Large Files Size - Increase complexity - Greater impact of failure - More Difficult recovery

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Database Administrator or Database Administration(DBA)

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Person or group in charge of the database

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Integrity Constraint

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a rule that data must follow in the database

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Security

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prevention of unauthorized acces

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Data Independence

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Can change structure of a database without changing the programs that access the database

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Forms

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Screen objects used to maintain, view, and print data from a database.

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Relation

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two-dimensional table in which entries are single-valued, each column has a distinct name, all values in a column are values of the same attribute, order of columns is immaterial, each row is distinct, Order of rows is immaterial.

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Relational Database

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Collection of tables

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Unnormalized Relation

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A structure that satisfies all properties of a relation except for the first item. Entries contain repeating groups; they are not single-valued

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Primary Key

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column or collection of columns of a table(relation) that uniquely identifies a given row in that table

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Query

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Question represented in a way that the DBMS can recognize and process

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Query-By-Example(QBE)

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Visual approach to writing queries. Users ask their questions using on-screen grid. Data appears on the screen in tabular form.

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Criteria

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Conditions that data must Satisfy

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Criterion

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Single Condition that data must satisfy. To enter a criterion for a field: include field in the design grid. Enter criterion in Criteria row for that field

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Comparison Operator

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Also Called relational operator. Used to find something other than an exact match. (=, , >=, <=, and NOT)

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Compound criteria/conditions

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AND and OR criterion

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AND Criterion

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both criteria must be true for the compound criteria to be true

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OR Criterion

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Either criteria must be true for the compound criterion to be true

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Computed/Calculated Field

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Results of a calculation on one or more existing fields

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To include a computed field in a Query:

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Enter a name for the computed field, followed by a colon, followed by an expression in one of the columns in the Field row

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Alternative Method

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Right-click the column in the field row, and then click Zoom to open the Zoom dialog box. Type expression in the Zoom dialog box

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Grouping

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Creating groups of records that share some common characteristics

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Sorting

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Listing records in query results in an ordered way

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Sort Key

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Field on which records are sorted

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Major sort key

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Also called the primary sort key. First sort field, when sorting records by more than one field

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Minor sort key

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Also called the secondary sort key. Second sort field, when sorting records by more than one field

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Update Query

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A query that changes data

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Delete Query

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Permanently deletes all records satisfying the criteria entered in the query

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Make-Table Query

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creates a new table using results of a query

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Relational Algebra

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Theoretical way of manipulating a relation database

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Select

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Takes horizontal subset of a table. Retrieves certain rows from an existing table and saves them as a new table. Includes the word WHERE followed by a condition example

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Project

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Takes a vertical subset of a table. Causes only certain columns to be included in the new table. Includes the word OVER followed by a list of the columns to be included.

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Join

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Allowed extraction of data from more than one table. Two tables being joined. Natural Join and Outer Join.

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Join Column

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Common column on which two table are joined

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Natural Join

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Joins records from each original table that is common to both tables

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Outer Join

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Joins records from each original table including records not common to both tables

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UNION of tables A and B

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Table contacting all rows that are either table A or table B in both tables A and table B

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INTERSECTION of tables A and B

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Table containing all rows that are common in both tables A and tables B

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Difference of tables A and B

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Reffered to as A minus B. Set of all rows that are in table A but that are not in table B.

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Union

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Two table are union compatiable when: - They have the same number of columns - Corresponding columns represent the sane type of data

Database Concepts 801 Ch. 1-2 – Flashcards

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