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DBMSS z

z z

The Database Management System (DBMS) is the software that manage (builds and maintains) the database. database This includes Adding, Deleting and Changing records in the database. The DBMS will also control access to the data. z

A financier user, for example, may not be able to view personnel data,, even though p g both finance and personnel p data are kept in the same database. ITM Lecture 5 Advanced Diploma (Thames College)

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DBMSS z

The DBMS makes it easier for programmers to develop application systems.

ITM Lecture 5 Advanced Diploma (Thames College)

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Functions Fu ct o s of o a DBMSS z What

are the functions performed by a DBMS? z Record d

C Creation and d Updates d z Record Selection by y Search Criteria z Minimize Data Redundancy z Security

ITM Lecture 5 Advanced Diploma (Thames College)

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Record eco d Creation C eat o and a d Updates z The

database is maintained by the user creating, deleting or amending records. z The Th D Database b M Management SSystem will ill also l allow the user to process selected groups of records, the whole file or individual records. z This is accomplished by selecting the required option from a menu displayed on the video screen or by keying in the relevant command from the keyboard. ITM Lecture 5 Advanced Diploma (Thames College)

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Record Selection by Search Criteria z z z

z z

Involve the extraction of information from the selected records according to specified search criteria. A database has searching facilities ranging from limited searches on keywords to full text searching. This facility provides the means of extracting from a large volume l off data d useful f l facts f which hi h could ld not possibly ibl b be found by physical search methods in sufficient time to make a decision decision. A query language is used to specify the search criteria. This language facilitates enquiries using English-style word to define commands, so greatly assisting users to find the information theyy are seeking. g ITM Lecture 5 Advanced Diploma (Thames College)

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Minimizee Data ata Redundancy edu da cy z If

a data element or record (e (e.g. g an employee address) appears twice in an organization's i ti ' records, d this thi is i called ll d Data D t Redundancy, since logically, it should not be necessary to hold the data twice, hence one copy py is redundant. z In a database, data redundancy should be eliminated, li i t d or att least, l t minimized i i i d andd this thi is the task of the DBMS. ITM Lecture 5 Advanced Diploma (Thames College)

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Securityy z The

Database Management System is also responsible for providing security for the d t b database, ensuring i against i t unauthorized th i d access and data corruption. z For

example, if many end-users are given access to common data,, there must be a wayy of controlling that access to ensure that no w users are able b to change g the data two simultaneously. ITM Lecture 5 Advanced Diploma (Thames College)

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Advantages dva tages of o Databases atabases z Reduces

data duplication which occurs using conventional file structure. z Avoids duplicating input data to update multiple p functionalityy independent p files holding the same date. z Offers Off r useful f l query r and d rreport p rt generation r ti languages. z Provides fast and flexible access to information information. ITM Lecture 5 Advanced Diploma (Thames College)

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Disadvantages sadva tages of o Database atabase z Data

structures in a database are complex and therefore takes a longer time to design andd iimplement. l t z Costs more than conventional file systems. y z Requires high caliber, experienced and specialized p i liz d p personnel. r l

ITM Lecture 5 Advanced Diploma (Thames College)

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Value Chain Model Value Chain Model: 價值鏈模式 z Highlights the primary or support activities adding a margin i off value l tto products d t or services i 突險企業中某些最佳應用競爭策略的特殊活動.服務 z

2008/4/2

Helps achieve a competitive advantage 有效加強競爭力

Information systems,organizations,management, and strategy

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