/SQL

Learning SQL

Learn SQl

Jayed Hossain Jibon Jayed Hossain Jibon Jayed Hossain Jibon Jayed Hossain Jibon Jayed Hossain Jibon Jayed Hossain Jibon

01. Create database and drop database

Solution 
create database learn_sql;
drop database learn_sql;

02. How to create table

Solution 
CREATE TABLE Customers (
    CustomerID serial PRIMARY KEY,
    CustomerName VARCHAR ( 100 ) UNIQUE NOT NULL,
    ContactName VARCHAR ( 20 ) NOT NULL,
    Address VARCHAR ( 100 ) NOT NULL,
    City VARCHAR ( 100 ) UNIQUE NOT NULL,
    PostalCode VARCHAR ( 100 ) UNIQUE NOT NULL,
    Country VARCHAR ( 100 ) UNIQUE NOT NULL
);

03. How to drop table

Solution 
drop table Customers;

04. Insert data into a table

Solution 
INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
VALUES ('Jibon Ahmed', '01987132107', '69/A, Dhaka', 'Dhaka', '1200', 'Bangladesh');

--- Multiple value insert
INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
VALUES 
('Jibon Ahmed',   '01987132107', '69/A, Dhaka', 'Dhaka', '1200', 'Bangladesh'),
('Jayed Hossain', 'Georg Pipps', 'Geislweg 14', 'Salzburg ', '5020 ', 'Austria');

SQL Query

Return all the columns from the Customers table

Syntax:
SELECT column1, column2, ...
FROM table_name;
Solution 
select * from customers

Return CustomerName, City from the Customers table

Solution 
select CustomerName, City from customers

The SELECT DISTINCT statement is used to return only distinct

Syntax:
SELECT DISTINCT column1, column2, ...
FROM table_name;
Solution 
select count(DISTINCT country) from customers;

SQL WHERE Clause

Syntax:
SELECT column1, column2, ...
FROM table_name
WHERE condition;

Select all customers from Bangladesh ?

SQL requires single quotes around text values
Solution 
SELECT * FROM Customers
WHERE Country='Bangladesh';

Select all customers with a CustomerID greater than 80:

Solution 
SELECT * FROM Customers
WHERE CustomerID > 80;

SQL ORDER BY Keyword

The ORDER BY keyword is used to sort the result-set in ascending or descending order.
Syntax:
SELECT column1, column2, ...
FROM table_name
ORDER BY column1, column2, ... ASC|DESC;

Sort the products from highest to lowest price:

Solution 
SELECT * FROM Products
ORDER BY Price DESC;

Sort the products alphatbetically by ProductName:

Solution 
SELECT * FROM Products
ORDER BY ProductName;

Sort the products by ProductName in reverse order

Solution 
SELECT * FROM Products
ORDER BY ProductName DESC;

Selects all customer sorted by the Country and CustomerName

Solution 
SELECT * FROM Customers
ORDER BY Country, CustomerName;

SQL AND Operator

Syntax :
SELECT column1, column2, ...
FROM table_name
WHERE condition1 AND condition2 AND condition3 ...;

Select all customers from Spain that starts with the letter 'G'

Solution 
SELECT * FROM Customers
where Country = 'Spain' and CustomerName LIKE 'G%';

Selects all fields from Customers where Country is "Germany" AND City is "Berlin" AND PostalCode is higher than 12000

Solution 
SELECT * FROM Customers
where Country = 'Germany' 
and City ="Berlin" 
and PostalCode > 12000;

Select all Spanish customers that starts with either "G" or "R"

Solution 
SELECT * FROM Customers
where Country = 'Spanish'
(CustomerName LIKE 'G%' OR CustomerName LIKE 'R%')

SQL OR Operator

Syntax :
SELECT column1, column2, ...
FROM table_name
WHERE condition1 OR condition2 OR condition3 ...;

Select all customers from Germany or Spain

Solution 
SELECT *
FROM Customers
WHERE Country = 'Germany' OR Country = 'Spain';

Select all Spanish customers that starts with either "G" or "R"

Solution 
SELECT * FROM Customers
WHERE City = 'Berlin' OR CustomerName LIKE 'G%' OR Country = 'Norway';

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