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Delete command is a data manipulation command which is used to remove records from a table. All records may be removed in one go, or a set of records may be deleted based on a condition.Remove specific rows from tableTo remove a specific row in the table, we need to mention where condition. Based on the condition, that particular row is deleted from the table.The syntax is as follows −delete from tablename where conditionFor example, Delete from employee where name=’sneha’;ExampleGiven below is an example to remove specific rows from table −create table employee(ename varchar(30), department varchar(20), age number(30), salary number(20)); ... Read More
Update command is a data manipulation command which is used to edit the records of a table. It may be used to update a single row based on a condition, all rows or set of rows based on the condition given by the user.It is used along with the SET clause, operationally, a WHERE clause may be used to match conditions −Example 1An example is given below for the use of update command −update table student set name=’sneha’ where branch=’CSE’;Example 2Given below is another example of the usage of update command −create table employee(ename varchar(30), department varchar(20)); insert into employee ... Read More
Insert command is data manipulation commands, which is used to manipulate data by inserting the information into the tables.This command is used to add records to a table. While inserting a record using the insert statement, the number of records being entered should match in the columns of the table. In case the number of items being created is less than the number of columns, the field names also need to be specified along with the insert statement.Insert commandIt is used for inserting the records into the table.The syntax is as follows −INSERT INTO table-name VALUES(field1, field2, ……..)ExampleGiven below is ... Read More
Select command is used to fetch the data in a set of records from a table, view or a group of tables, views by making use of SQL joins.Retrieval of data using SQL statements can be done by using different predicates like −WhereGroup ByHavingOrder ByThe simplest example of a select statement where in a user wants to, retrieve all the records of a table, can be performed by using '*'.First let's create and insert the data in table before retrieving the data using select command −Step 1create table student(name char(30), regno number(10), branch char(20), age char(10));The output will be as ... Read More
A file system is a method of storing and organizing the computer files and the data they contain to make it easy to find and access them.Characteristics of file systemThe characteristics of file system are as follows −It is a group of files for storing the data of an organization.Each file is independent from one another.Each file is called a flat file.Files are designed by using the program written in programming languages such as C, C++.Disadvantages of file processing systemThere are so many disadvantages in the file processing system. These are explained below −Separated and isolated data.Duplication of data − ... Read More
Before understanding the difference between data and information, let’s have a look at the definitions of data and information with an example.DataData is the raw material that can be processed for any computing machine.For example − Employee name, Product name, Name of the student, Marks of the student, Mobile number, Image etc.InformationInformation is the data that has been converted into more useful or intelligent form.For example: Report card sheet.The information is needed for the following reasons −To gain knowledge about the surroundings.To keep the system up to date.To know about the rules and regulations of the society.KnowledgeThe human mind purposefully ... Read More
Let’s discuss flat and database definition before understanding the difference between flat files and databases.Flat filesA flat file contains records which have no structured interrelationship. They are typically called as a text file, where all word processing, structure characters and markup have been removed. A flat file represents a table with a single record per line. Generally, it is a type of database that stores data in a plain text format.DatabaseThe related information when placed in an organized form that makes a database or an organized collection of related information is called a database.For example − Dictionary, Telephone directory etc.DifferencesFollowing ... Read More
Electricity tariff is defined as the rate at which electrical energy is supplied to a consumer.Types of Tariff in ElectricityThe commonly used electricity tariffs are as follows −Simple Tariff – When there is a fixed rate per unit of energy consumed, it is known as simple tariff or uniform rate tariff. In case of simple tariff, the price charged per unit is constant i.e. it does not change with increase or decrease in number of units consumed.Flat Rate Tariff – When different types of consumers are charged at different uniform per unit rates, it is known as flat rate tariff. In ... Read More
An electrical power system is a network of interconnected electrical devices, which are used to generate, transmit, distribute and utilise the electrical power.A typical electrical power system has following main components −Generating StationTransmission SystemDistribution SystemElectrical LoadGenerating StationIn the single line diagram, the GS represents the generating station where electrical power is produced by three-phase parallel connected alternators. The usual generation voltage is 11 kV (in India). For economic considerations the generation voltage is stepped up to high voltages (say 132 kV) using 3-phase transformers for the transmission.Transmission SystemThe electrical transmission system is divided into two types depending on the voltage ... Read More
The voltage levels or voltage ratings are defined and classified by various national and international standards and also by some electrical utility companies.In general, an electrical professional comes across the terms LV / LT, MV, HV / HT, EHV / EHT and UHV in our day-to-day professional lives.Voltage Rating StandardsThe Indian Electricity Rules, 1956, the following were the voltage limits of power system and equipment −Low Voltage (LV) − Less than or equal to 250 V.Medium Voltage (MV) − Less than or equal to 650 V.High Voltage (HV) − Less than 33 kV.Extra-High Voltage (EHV) − More than 33 kV.However, ... Read More