Database guide in 2021

Data is one of the most important components of geospatial technology and perhaps any other industry. Data management is now taken seriously in all industries, so knowledge in this discipline is essential for an IT professional's careers. This article series is intended to be a one-stop guide in which we'll cover the topic inside and out, starting with the question "What is data?" and ending with the study and application of geospatial queries.





Basic Database Concepts

What is data?





Data can be any information that is stored for the purpose of future reference. This information can include numbers, text, audio and video footage, location, dates, and more. It can be written down on paper or stored on your computer's hard drive or even in the cloud.





What is a database?





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Sample Information Table

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Relationship between two columns

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Creating a new database for the project

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CREATE DATABASE <database_name>
      
      



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Creating a user table

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CREATE TABLE <table_name> (
<column_1> <datatype>,
<column_2> <datatype>,
..
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<column_n> <datatype>
PRIMARY KEY (<column>)
);
      
      



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INSERT INTO <tablename> (column1, column2, column3,...) VALUES (value1, value2, value3,...);
      
      



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INSERT INTO users(name, employed, address) VALUES ('Sheldon Cooper', true, 'Pasadena');
      
      



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select <column1, column2 ,...> from <tablename> 
      
      



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select <column1, column2 ,...> from <tablename> limit 20
      
      



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select * from <tablename>
      
      



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select * from <tablename> where <key> = <value>
      
      



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--Retrieving Specific columns for all users
select name,employed from users
--Retrieving all columns for all users
select * from users
--Retrieving all columns for first 3 users
select * from users limit 3
--Retrieving all columns for all users where employed = true
select * from users where employed = true
      
      



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UPDATE <tablename> 
SET <column1> = <value1>, <column2> = <value2> 
      
      



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UPDATE <tablename> 
SET <column1> = <value1>, <column2> = <value2>
WHERE <column> = <value> 
      
      



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-- Make all rows as  employed = true
update users set employed = true
-- change employed = false for entries with address = 'nebraska'
update users set employed = false where address = 'nebraska'
      
      



Updating records

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-- Deleting all entries 
Delete from <tablename> 
-- Deleting entries based on conditions
Delete from <tablename> where <column> = <value> 
      
      



-- Deleting all entries 
Delete from users
-- Deleting entries based on conditions
Delete from users where employed = false
      
      



Removing records from a table

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