Sunday, September 14, 2008

int survey #8...

**BACKGROUND OF POSTGRESQL

PostgreSQL is an object-relational database management system (ORDBMS). It is released under a BSD-style license and is thus free software. PostgreSQL is not controlled by any single company, but relies on a global community of developers and companies to develop it.The mixed-capitalization of the PostgreSQL name can confuse some people on first viewing. The several pronunciations of 'SQL' can lead to this confusion. However, the PostgreSQL Core Team announced in 2007 that the product would continue to be named PostgreSQL. The name refers to the project's origins as a "post-Ingres" database, the original authors having also developed the Ingres database.

PostgreSQL includes built-in support for B+-tree, hash, GiST and GiN indexes. In addition, user-defined index methods can be created, although this is quite an involved process. Indexes in PostgreSQL also support the following features:

*PostgreSQL is capable of scanning indexes backwards when needed; a separate index is never needed to support ORDER BY field DESC.
*Expression indexes can be created with an index of the result of an expression or function, instead of simply the value of a column.
*Partial indexes, which only index part of a table, can be created by adding a WHERE clause to the end of the CREATE INDEX statement. This allows a smaller index to be created.
*The planner is capable of using multiple indexes together to satisfy complex queries, using temporary in-memory bitmap index operations.

**DIFFERENCE BETWEEN MEMORY VARIABLE AND DATABASE FIELD

Memory variable is an attribute of a physical or an abstract system which may change its value while it is under observation while database fields are the basic units of data storage, and each field typically contains information pertaining to one aspect or attribute of the entity described by the database.

**DIFFERENCE BETWEEN DATABASE RECORD AND DATABASE FIELD

The difference between database field and database record is that, database fields are the basic units of data storage, and each field typically contains information pertaining to one aspect or attribute of the entity described by the database while database records are organized into tables that include information about relationships between its various fields.

Friday, September 5, 2008

ERRATUM

Sir, hi! ;)

i made this post just to make corrections.. i just noticed that my BLOG NUMBERING is not right. but then, i opted not to change it since the dates will be changed to0. sorry sir. ;)

take care and Godblesssss... ;)

int survey#8..

**WHAT IS NORMALIZATION?

**ANSWER:

Database normalization, sometimes referred to as canonical synthesis, is a technique for designing relational database tables to minimize duplication of information and, in so doing, to safeguard the database against certain types of logical or structural problems, namely data anomalies. For example, when multiple instances of a given piece of information occur in a table, the possibility exists that these instances will not be kept consistent when the data within the table is updated, leading to a loss of data integrity. A table that is sufficiently normalized is less vulnerable to problems of this kind, because its structure reflects the basic assumptions for when multiple instances of the same information should be represented by a single instance only.

Higher degrees of normalization typically involve more tables and create the need for a larger number of joins, which can reduce performance. Accordingly, more highly normalized tables are typically used in database applications involving many isolated transactions while less normalized tables tend to be used in database applications that need to map complex relationships between data entities and data attributes (e.g. a reporting application, or a full-text search application).

Database theory describes a table's degree of normalization in terms of normal forms of successively higher degrees of strictness. A table in third normal form (3NF), for example, is consequently in second normal form (2NF) as well; but the reverse is not necessarily the case.

Although the normal forms are often defined informally in terms of the characteristics of tables, rigorous definitions of the normal forms are concerned with the characteristics of mathematical constructs known as relations. Whenever information is represented relationally, it is meaningful to consider the extent to which the representation is normalized.

Thursday, July 17, 2008

int survey #6..

**CHOOSE ONE DBMS SOFTWARE AND DISCUSS IT'S STRUCTURE AND HOW ITS DATA ENTRY FORMS ARE CREATED.

ORACLE


The Oracle RDBMS stores data logically in the form of table spaces and physically in the form of data files. Table spaces can contain various types of memory segments; for example, Data Segments, Index Segments etc. Segments in turn comprise one or more extents. Extents comprise groups of contiguous data blocks. Data blocks form the basic units of data storage. At the physical level, data-files comprise one or more data blocks, where the block size can vary between data-files.

Oracle database management tracks its computer data storage with the help of information stored in the SYSTEM table space. The SYSTEM table space contains the data dictionary — and often (by default) indexes and clusters. (A data dictionary consists of a special collection of tables that contains information about all user-objects in the database). Since version 8i, the Oracle RDBMS also supports "locally managed" table spaces which can store space management information in bitmaps in their own headers rather than in the SYSTEM table space (as happens with the default "dictionary-managed" table spaces).

If the Oracle database administrator has instituted Oracle RAC (Real Application Clusters), then multiple instances, usually on different servers, attach to a central storage array. This scenario offers numerous advantages, most importantly performance, scalability and redundancy. However, support becomes more complex, and many sites do not use RAC. In version 10g, grid computing has introduced shared resources where an instance can use (for example) CPU resources from another node (computer) in the grid.

The Oracle DBMS can store and execute stored procedures and functions within itself. PL/SQL (Oracle Corporation's proprietary procedural extension to SQL), or the object-oriented language Java can invoke such code objects and/or provide the programming structures for writing them.

Sunday, July 6, 2008

int survey #5...

**CONTRAST THE DIFFERENT DATABASE MODEL & DISCUSS THE MANAGEMENT ACT DBMS PERFORMS UPON DATA.
**Answer:

Hierarchical

The hierarchical data model organizes data in a tree structure. There is a hierarchy of parent and child data segments. This structure implies that a record can have repeating information, generally in the child data segments. To create links between record types, the hierarchical model uses Parent Child Relationships. These are a 1:N mapping between record types. This is done by using trees.

Network

Some data were more naturally modeled with more than one parent per child. So, the network model permitted the modeling of many-to-many relationships in data. In 1971, the Conference on Data Systems Languages (CODASYL) formally defined the network model. The basic data modeling construct in the network model is the set construct. A set consists of an owner record type, a set name, and a member record type. A member record type can have that role in more than one set, hence the multiparent concept is supported. An owner record type can also be a member or owner in another set.

Relational

(RDBMS - relational database management system) A database based on the relational model developed by E.F. Codd. A relational database allows the definition of data structures, storage and retrieval operations and integrity constraints. In such a database the data and relations between them are organised in tables. A table is a collection of records and each record in a table contains the same fields.

Object/Relational

Object/relational database management systems (ORDBMSs) add new object storage capabilities to the relational systems at the core of modern information systems. These new facilities integrate management of traditional fielded data, complex objects such as time-series and geospatial data and diverse binary media such as audio, video, images, and applets. By encapsulating methods with data structures, an ORDBMS server can execute comple x analytical and data manipulation operations to search and transform multimedia and other complex objects.

Object-Oriented

Object DBMSs add database functionality to object programming languages. They bring much more than persistent storage of programming language objects. A major benefit of this approach is the unification of the application and database development into a seamless data model and language environment. As a result, applications require less code, use more natural data modeling, and code bases are easier to maintain. Object developers can write complete database applications with a modest amount of additional effort.This one-to-one mapping of object programming language objects to database objects has two benefits over other storage approaches: it provides higher performance management of objects, and it enables better management of the complex interrelationships between objects.

Semistructured

In semistructured data model, the information that is normally associated with a schema is contained within the data, which is sometimes called ``self-describing''. In such database there is no clear separation between the data and the schema, and the degree to which it is structured depends on the application. In some forms of semistructured data there is no separate schema, in others it exists but only places loose constraints on the data. Semi-structured data is naturally modeled in terms of graphs which contain labels which give semantics to its underlying structure.

Semistructured data has recently emerged as an important topic of study for a variety of reasons. First, there are data sources such as the Web, which we would like to treat as databases but which cannot be constrained by a schema. Second, it may be desirable to have an extremely flexible format for data exchange between disparate databases. Third, even when dealing with structured data, it may be helpful to view it as semistructured for the purposes of browsing.

Associative

The associative model divides the real-world things about which data is to be recorded into two sorts:
Entities are things that have discrete, independent existence. An entity’s existence does not depend on any other thing. Associations are things whose existence depends on one or more other things, such that if any of those things ceases to exist, then the thing itself ceases to exist or becomes meaningless.
An associative database comprises two data structures:
1. A set of items, each of which has a unique identifier, a name and a type.
2. A set of links, each of which has a unique identifier, together with the unique identifiers of three other things, that represent the source source, verb and target of a fact that is recorded about the source in the database. Each of the three things identified by the source, verb and target may be either a link or an item.

Entity-Attribute-Value (EAV)

The best way to understand the rationale of EAV design is to understand row modeling (of which EAV is a generalized form).Conceptually an EAV design involves a single table with three columns, an entity (such as an olfactory receptor ID), an attribute (such as species, which is actually a pointer into the metadata table) and a value for the attribute (e.g., rat). In EAV design, one row stores a single fact. In a conventional table that has one column per attribute, by contrast, one row stores a set of facts. EAV design is appropriate when the number of parameters that potentially apply to an entity is vastly more than those that actually apply to an individual entity.

Context

The context data model combines features of all the above models. It can be considered as a collection of object-oriented, network and semistructured models or as some kind of object database. In other words this is a flexible model, you can use any type of database structure depending on task. Such data model has been implemented in DBMS ConteXt.

END

int survey #4...

**IDENTIFY AT LEAST 10 DBMS SOFTWARES WITH THEIR CORRESPONDING DEVELOPER. THEN CHOOSE 1 AND BRIEFLY TELL HOW DOES DBMS HANDLE OR ACCOMMODATE DATA INPUT.


Oracle Database
Developed by Oracle Corporation

IBM DB2
Developed by IBM

FileMaker
Developed by FileMaker Inc. Latest release

Firebird (database server)
Developed by Firebird Project

Ingres
Developed by Ingres Corporation

Microsoft Access

Developed by Microsoft

Microsoft SQL Server

Developed by Microsoft

MySQL
Developed by Sun Microsystems

PostgreSQL
Developed by PostgreSQL Global Development Group

OpenEdge Advanced Business Language
Developed by Progress Software Corporation

__________________________________________________


Microsoft SQL Server


The data in the database are stored in primary data files with an extension .mdf. Secondary data files, identified with an .ndf extension, are used to store optional metadata. Log files are identified with the .ldf extension.

The main unit of data storage is a database, which is a collection of tables with typed columns. SQL Server supports different data types, including primary types such as Integer, Float, Decimal, Char (including character strings), Varchar (variable length character strings), binary (for unstructured blobs of data), Text (for textual data) among others.SQL Server also makes server statistics available as virtual tables and views (called Dynamic Management Views or DMVs). A database can also contain other objects including views, stored procedures, indexes and constraints, in addition to tables, along with a transaction log. An SQL Server database can contain a maximum of 231 objects, and can span multiple OS-level files with a maximum file size of 220 TB.

Storage space allocated to a database is divided into sequentially numbered pages, each 8 KB in size. Page type defines the data contained in the page - data stored in the database, index, allocation map which holds information about how pages are allocated to tables and indexes.

The main mode of retrieving data from an SQL Server database is querying for it. The query is expressed using a variant of SQL called T-SQL, a dialect Microsoft SQL Server shares with Sybase SQL Server due to its legacy. The query declaratively specifies what is to be retrieved. It is processed by the query processor, which figures out the sequence of steps that will be necessary to retrieve the requested data. The sequence of actions necessary to execute a query is called a query plan.

END

Sunday, June 29, 2008

int survey #3..

**INTERRELATE

sir, since i interrelated my answers in the 2nd survey, i need not interrelate it again?? hehehe.. plz answer. ;))


**QUESTION: for what??? ;))
**Answer:

The things that we input in the computer are data or what we call as unprocessed information. These data will undergo different processes. First, it will be stored in the storage devices of the computer. Then, it will be made as information. But why do we have to process these data? FOR WHAT??? It is processed so that it will be of better use. Everything needs improvement and so thus the data that we use. Another reason is because it becomes a source of the students, etc. And lastly, since change is constant, later on, these 'information' will be used as data again. It's a cycle.

**NEW ANSWER
We process data for it will then be our guide or basis for decision making. ;))

END

Sunday, June 22, 2008

int survey #2

**DISCUSS AND INTERRELATE THE FOLLOWING:

**DATA
-It is what the user inputs. It is the raw information that may consists of words, numbers, images and symbols.

**DATA TYPE
-A data type classifies the data into its kind. It may be integers, floating-point numbers, and alphanumeric strings.

**DATA STRUCTURE
-Data structure is a way of storing data in a computer. It organizes related pieces of information. Examples are, files, lists, arrays, records, trees, etc.

**DBMS
-A database management system (DBMS) is computer software designed for managing databases. It is also a collection of programs that enables you to store, modify, and extract information from a database.



______________________________________________________


A DATA TYPE tells the computer what kind of DATA is being "input" by the user. These DATA have a way of storage and that is called DATA STRUCTURE. A DBMS is categorized according to their DATA STRUCTURES.


______________________________________________________

Saturday, June 21, 2008

int survey #1


**QUESTION: What is the importance of an operating system?
**Answer: It manages all the functions of the softwares. Without it the computer will not work.

[new answer]

** 1. Operating system is just a designated word. Before, there was a system but it was being operated manually. Then, through the development of technology, computers has been miniaturized. Softwares also evolved and so, it need not be operated manually, thus, it is now called, operating system or OS. ;))

__________________________________________________



**QUESTION: Differentiate Operating system from an application software.
**Answer: Operating system manages all the functions done by all the software while an application software manages only one software.

[new answer]

** 1. Operating system is a software which basically operates the system. It is just a designated word. On the other hand, an application software, are those softwares which help the users. It works under the OS.
** 2. OS manages all the hardwares such that it could be able to provide services to application softwares. Ex.When a word processor (application software) wants to print something, the OS, "tells" the printer to print.

__________________________________________________


**QUESTION: What do you intend to do in life? Why did you enroll in this course?
**Amswer: Today, competition is very tight. I noticed that almost all the jobs requires computer literacy. I decided to be an information technology student because i know that if I will be an IT graduate, i will have an edge over other grads since I know how to operate computers. Therefore, my plans in life would be, to have my own business that deals with computers. ;))


__________________________________________________


**QUESTION: Describe yourself.
**Answer: Im a God-fearing person and I believe that everything happens upon His will. I temporarily reside at Orchids, Daro. I have a home of Amlan, Negros Oriental. I surf the net a lot and I'm also a text addict. I also love to write for I could express my feelings through it. I work for The NORSUnian, the official weekly publication of NORSU. Iam a business manager and at the same time a senior writer there. Lastly, I believe that "An intelligent man knows when to listen." By the way sir, I'm Maria Margarita Narvasa but you can call me marga, mary or bewii. ;))