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Ch2 Data Organization and Data Control - Coggle Diagram
Ch2 Data Organization and Data Control
2.2 Data Control
Data validation
The process of comparing data with a set of rules and values to make sure that the data is reasonable and valid.
Can detect some invalid data in source documents
Validity check
Range check
Fixed value check
Field the length check
Format check
Type check
Check digit
Field presence check
Data verification
Method for data verification
Input data twice
Double Data Entry
Control used to check whether the inputted data matches that in the source document
2.4 Database Management System (DBMS)
DBMS provides functions :
~ Manage the database structure
~ Store, organize and retrieve data in a database
Application of DBMS
Database server
Small office and personal use
Basic Functions to Organize Tables
Modify table
Delete table
Create table
Essential Features
Index
Data Entry Forms
Sort
Query Froms
Filter
Reports
2.3 Data Hierarchy
Database > Table > Record > Field
Record
Collection information of related fields
The data in a key field can be used to uniquely identify one particular record from the others
Table
Collection of related records with identical record structures
All records in table have unique and different values in key field
Field
Smallest unit of data
Can be type: Numeric text, date,Boolean
Database
Collection of related tables
May link records from different tables
2.5 File Access Modes
Sequential Access mode
E.g. Magnetic tape
Storage backup
Average Reliability and Durability
Very high portable
Highly variable
Very low cost
Direct access mode
E.g. Hard disk
Low portable and. cost
Secondary storage
The seek time are Short and predictable
Very high reliability and durable
2.1 Data Input and Sources of Error
Data input
e.g. keyboard, sensors
During data entry
Mistake may be made
Sources of errors
Transcription error
Read or typed in incorrectly
Transposition error
Two consecutive digits are swapped
Data source error
Provide incorrect data
Garbage-in-garbage-out (GIGO)
Erroneous data always produces information, waste human resources while producing useless information.