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What is a Database? What is SQL language? - Definition and Explanation

, January 01, 2020 WAT
Last Updated 2020-07-29T16:59:58Z
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What is database system?

Database

The word Database means a collection of data.



Advantages of database:

  • Extremely fast data can be presented.
  • Data can be managed with the utmost efficiency
  • Preservative data can be updated later
  • Database information can be sorted as ascending and descending
  • Processing is accelerated
  • Processing is independent


Database Disadvantages:

  • Processing is often slow due to incorrect data
  • Some incorrect data can destroy the entire database
  • Experienced manpower needs to be maintained
  • Data security needs to be maintained


Database Components - Data: The data that we have provided in the form of inputs in different fields of the above table and shown in the figure is called data. Data is the most important thing in the database. Field: The name at the top of each column in the image above is called Field. This is basically the smallest part of the record. The figure shows the two fields neatly in si and name. Records: Records are made up of many fields. Usually, we consider a whole row as a record. In the figure - the record is specified.

Data Entity and Data Attribute



Data Entity: Data Entity NTT is the main unit required for the ideal categorization of real or non-real objects. The NTT set is somewhat homogeneous, the assembly of the NTT. For example, the data files in a database are called NTT sets.



Data attribute: 

Each field in the record of a data file within a database is called an attribute consisting of a number of characters. For example - Employee file fields can be name, surname, basic salary. So here name, surname, salary will be the attribute.


Primary key, foreign key, and composite primary key


A file consists of one or more fields. Fields usually have a field whose data is unique, that is, each of the data in that field is different. So a field in a file that does not match one data with other data i.e. each data is different is called the primary key field. For example, the roll number of the candidates in any exam, the account number of the customers in any one bank.


Foreign Key (Secondary Key):

If one field of a file in a database matches the primary key field of another file, then that field is called a foreign key field. In other words, if a column in a data table coincides with the primary key in another data table, then the key field corresponding to that primary key is called a foreign key.

Composite Primary Key Fields: In many cases, a database file does not have a specific primary key field. In this case, the primary key field is selected from a combination of multiple individual fields. The primary key, which consists of two interconnected fields in a thread, is called the composite primary key field.

Database Management System (DBMS)

Database Management System:


Database Management System or DBMS is software that is used to create, modify, save, and manage databases.
Example: There are many database management software in use nowadays. Such as -
  • FoxPro
  • Ms. Access
  • Oracle

The primary functions of DBMS are-


  • Create a database as required.
  • User control.
  • Input new data.
  • Detecting and correcting spelling and numbering of data.
  • Exclude unnecessary data or records.
  • Final editing work.
  • Search and use data or records as needed.
  • If necessary, format the database based on any field, alphabetically, numerically, by title or title or in some other way.
  • Create reports and print the required database.
  • Provide data security.
  • Saving data.

What is RDBMS? RDBMS feature


Relational Database Management System is abbreviated as RDBMS. In this case, the database has two or more data tables and the relationship between the data tables is based on which field. Important software for creating relational databases are Microsoft Access, Microsoft Visual FoxPro, Oracle, SQL Server, My SQL, Base, etc.

Relational Database Management System Features:

Data entry can be done very easily by creating a data table.
Information can be easily exchanged from one database to another.
Necessary data can be easily found from numerous data.
Data entry can be controlled with the help of data validation.
Reports and labels of various formats can be easily created and printed.
Numerical data can do fine mathematical work.
Necessary charts or graphs can be created on the basis of data.
Graphical data entry forms can be easily created.
It can be used to fetch data from other programs.
Links to files from other programs can be established.
Application software can be easily created.

Relational Database Management System Usage:
In the case of airline ticketing and flight schedules
In case of keeping customer accounts in banks and insurance
For keeping records of patients in the hospital
In electronic commerce
In the electronic payment system
In creating student information system in educational institutions
In preserving population data
Creating an organization's inventory management system
In all the other cases where you have to work with huge data


Data types for different types of fields in the database

Computers work with data. The type or nature of this data can be of different types. 
The different types of data types are discussed below-
Text:
Letters, symbols, or numbers can be used in text or character type fields. A maximum of 255 characters can be used in this field.
Numeric:
Numbers can be used in numeric type fields. Mathematical operations such as addition, subtraction, multiplication, division, etc. can be performed based on this field.
Yes / No or Rational
This field may contain information such as yes/no or true/false. This type of field is called logical field. This type of field takes up 1 bit of space in memory.
Date / Time:
This field is used for date or time. Dates and times can be of different formats. This field requires 8 bytes of memory.
Memo
This field is used for descriptive writing or description. 65,535 characters can also be written in this field.
Currency:
This field is used to input currency or money related data. Mathematical calculations can be made on the data in this field. This field requires 8 bytes of memory.
Hyperlink t
Hyperlinks are used for data entry in any field. To take data input from a file, you have to hyperlink that file.

Database relation

 The relation of data from one data table to the data of one or more other data tables is called relation. The relationship between the data tables can be as follows-

  • One to One Relation
  • One to Many Relation
  • Many to One Relation
  • Many to Many Relation

One to One Relation:

If a record of a file within a database is related to only one record of another file, it is called a One to One relation.
For example, the fields in the student's examination file in the database of the students' information in the college - name, roll number, the number obtained and the fields in the file of the student's personal information - roll number, father's name, phone number, address, etc. Here a record of the test file relates to a record of the personal information file.

One to Many Relation:

If a record in a database is related to more than one record in another file, then it is called a One to Many relation. Suppose, in any office, different suppliers deliver different products. In this case, a database called Supplier has been created for subscribers and another database called Order has been created for information related to the supply of goods. Usually, a sapsnier offers a variety of products. As a result, a Supplier database stores multiple transactions in the Orders database as opposed to that number. In this case, if you want to establish a relationship between the two databases, it will be a one to many relationships.

Many to One Relational:

If more than one record of a file is related to a record of another file in a database, it is called a Many to One relation. For example, a business organization has two databases called Phone.dbf and Office.dbf. There are multiple phone numbers for each office and the relational structure of Office dbf with Phone dbf will be a Many to One relation.
Many to Many Relation:
If more than one record of a data file included in a database is related to more than one record of another data file then it is called a Many to Many relations. To create a many to many relationships, you have to create a third table.


Indexing


Indexing is the process of sorting the input records in a data file according to certain rules. File records are arranged in ascending or descending order so that the user can quickly find any data from the database. Indexing is the process of arranging database records in such a reasonable order. The record of the data file can be sorted by sorting, but the sorted file is saved under another name and if any record of the database is modified or added later, it will not be updated in the sorted file.
 The
first table is the state before indexing. And the second table is the next state of indexing. Here the Name field is indexed in the Ascending order.


Advantages of indexing:

Easily find data.
Data can be easily found after indexing.
Automatically update data
After indexing, when a new record is an input into the database, the index file is automatically updated.
Increase the efficiency of various operations in the database
Indexing is done on the records in the database to complete various operations like Searching, Shorting, Queries, etc. very quickly.
Keep the original file unchanged
Index files can be sorted in different ways without making any changes to the original database file.

Disadvantages:

In addition to having different types of advantages, there are also some disadvantages of indexing. If indexing is done on a field, the program automatically updates the index file when editing the data in the data table or adding new records to the data table and this takes very little time. Indexing takes at least two or more fields. As a result, it is difficult to keep track of the index file. In this case, the index file also occupies a lot of space in memory. 


DDL, DML

DDL:

The language used in database management systems for data storage, processing, database file creation, database file modification, database file deletion, etc. is called Data Definition Language or DDL. DDL is one of the most important of the various benefits that database management systems provide to database users.


The main functions of DDL are-


  1. Create tables and other objects needed to store data in the database.
  2. Changing tables or other objects.
  3. Deleting a table or other object.

SQL is a Data Definition Language. A table or other object is created with the Create command of SQL, a table or another object is changed with the Alter command, and a table or other object is deleted with the Drop command.



DML:

The short form of Data Manipulation Language is called DML. The language used to insert, update or delete data in the database is called Data Manipulation Language or DML.

Three things can be done with the help of DML.

Insert operation for any new information in the database
Delete operation for deleting any information from the database
Update Operation for updating any information in the database


Formatted report


Reports are prepared from the database to print the required data from the database. Formatting a report by adding some additional features to the report to make it easier for the user to understand is called a formatted report.

The different parts of the formatted report are -
  • Report Header
  • Page Header
  • Detail
  • Page Footer
  • Report Footer

Report Header: The title or headline of the report
is displayed through this part. Running titles can be changed or new titles can be added. When printing, the title is printed on the first page.

Page Header: The
data heading on the top of each page is displayed here. For example- L / C No, Quantity, item code etc. is a field which is displayed on every page as data heading.

Detail:
The results or data of the report are displayed in this section.

Page Footer:
If there is a need to add a part at the bottom of each page of the report, it is added to this part. E.g. page number, or any sign (e.g. PTO) etc.

Report Footer:
The summary of the entire report is displayed in this section. Such as- total sum, number of records, number of pages etc.


Report


The data in the data table is arranged in different ways. Reporting is the process of displaying the required data from the database in the form of a report. Report 6 types. E.g.

  1. Detail Reports
  2. Summary Reports
  3. Cross Tabulation Reports
  4. Reports with Graphics and Chart
  5. Reports with Forms
  6. Reports with Labels.


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