 
-- 2. SQL Queries
-- Retrieve the first 10 records from the dataset 
SELECT * FROM transactions 
LIMIT 10;

-- Calculate the total number of transactions in the dataset 
SELECT COUNT(*) AS Total_Transactions 
FROM transactions;

-- Find the total revenue generated from online sales
SELECT SUM(Total_Price) AS Total_Revenue 
FROM transactions;

-- Identify the top 5 best-selling products by quantity sold 
SELECT Product_Name, SUM(Quantity) AS Total_Quantity 
FROM transactions 
GROUP BY Product_Name 
ORDER BY Total_Quantity DESC 
LIMIT 5;

-- Calculate the average unit price of products sold
SELECT AVG(Unit_Price) AS Average_Unit_Price 
FROM transactions;

-- Determine the total sales revenue generated by each country.
SELECT Country, SUM(Total_Price) AS Total_Revenue 
FROM transactions 
GROUP BY Country;

-- Find the total quantity of products purchased by each customer.
SELECT Customer_ID, SUM(Quantity) AS Total_Quantity 
FROM transactions 
GROUP BY Customer_ID;

-- Identify the most common payment method used for transactions.
SELECT Payment_Method, COUNT(*) AS Total_Usage 
FROM transactions 
GROUP BY Payment_Method 
ORDER BY Total_Usage DESC 
LIMIT 1;

-- 3. Data Management:
-- Create customer_info table
CREATE TABLE customer_info (
  Customer_ID INTEGER PRIMARY KEY,
  Customer_Name VARCHAR(75),
  Email VARCHAR(45)
);

-- Insert sample data into customer_info table
INSERT INTO customer_info (Customer_ID, Customer_Name, Email) VALUES
(101, 'John Mwakazi', '[email protected]'),
(102, 'Islamiat Adeyawo', '[email protected]'),
(103, 'Alice Omondi', '[email protected]'),
(104, 'Bob Waswa', '[email protected]'),
(105, 'Joy Ishua', '[email protected]');

-- for testing: display table
-- SELECT * FROM customer_info;

-- Add Discount column to transactions table
ALTER TABLE transactions
ADD COLUMN Discount DECIMAL;

-- Update Discount column with 10% of Total_Price
UPDATE transactions
SET Discount = Total_Price * 0.10;

-- for testing display transactions
-- SELECT * FROM transactions;

-- Delete transactions with Quantity of 0 or negative values
DELETE FROM transactions
WHERE Quantity <= 0;

-- 4. Joining Tables  and displaying result
SELECT 
  transactions.Transaction_ID,
  transactions.Customer_ID,
  transactions.Transaction_Date,
  transactions.Product_ID,
  transactions.Product_Name,
  transactions.Unit_Price,
  transactions.Quantity,
  transactions.Total_Price,
  transactions.Country,
  transactions.Payment_Method,
  transactions.Discount,
  customer_info.Customer_Name,
  customer_info.Email
FROM transactions
INNER JOIN customer_info ON transactions.Customer_ID = customer_info.Customer_ID;

-- 5.SQL Functions
-- Total Price for each transaction
SELECT Unit_Price * Quantity AS Total_Price
FROM transactions;

-- Extract the month and year from the 'Transaction_Date' column.
SELECT
  Transaction_Date,
  DATE_FORMAT(Transaction_Date, '%m') AS Transaction_Month, -- Extract month
  DATE_FORMAT(Transaction_Date, '%Y') AS Transaction_Year -- Extract year
FROM 
  transactions;
  
-- Concatenate the 'Product_Name' and 'Country' columns to create a new column 'Product_Location'.
SELECT 
 Product_Name,
 Country,
 CONCAT(Product_Name, ' - ', Country) AS Product_Location
FROM 
  transactions;

created 1 year ago by Kelly Grace

MySQL online editor

Write, Run & Share MySQL queries online using OneCompiler's MySQL online editor and compiler for free. It's one of the robust, feature-rich online editor and compiler for MySQL. Getting started with the OneCompiler's MySQL editor is really simple and pretty fast. The editor shows sample boilerplate code when you choose language as 'MySQL' and start writing queries to learn and test online without worrying about tedious process of installation.

About MySQL

MySQL is a open-source, free and very popular relational database management system which is developed, distributed and supported by Oracle corporation.

Key Features:

Open-source relational database management systems.
Reliable, very fast and easy to use database server.
Works on client-server model.
Highly Secure and Scalable
High Performance
High productivity as it uses stored procedures, triggers, views to write a highly productive code.
Supports large databases efficiently.
Supports many operating systems like Linux*,CentOS*, Solaris*,Ubuntu*,Windows*, MacOS*,FreeBSD* and others.

Syntax help

Commands

1. CREATE

CREATE TABLE table_name (
                column1 datatype,
                column2 datatype,
                ....);

Example

CREATE TABLE EMPLOYEE (
  empId INTEGER PRIMARY KEY,
  name TEXT NOT NULL,
  dept TEXT NOT NULL
);

2. ALTER

ALTER TABLE Table_name ADD column_name datatype;

Example

INSERT INTO EMPLOYEE VALUES (0001, 'Dave', 'Sales');

3. TRUNCATE

TRUNCATE table table_name;

4. DROP

DROP TABLE table_name;

5. RENAME

RENAME TABLE table_name1 to new_table_name1;

6. COMMENT

Single-Line Comments:

 --Line1;

Multi-Line comments:

   /* Line1,
   Line2 */

DML Commands

1. INSERT

INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...);

Note: Column names are optional.

Example

INSERT INTO EMPLOYEE VALUES (0001, 'Ava', 'Sales');

2. SELECT

SELECT column1, column2, ...
FROM table_name
[where condition];

Example

SELECT * FROM EMPLOYEE where dept ='sales';

3. UPDATE

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

Example

UPDATE EMPLOYEE SET dept = 'Sales' WHERE empId='0001';

4. DELETE

DELETE FROM table_name where condition;

Example

DELETE from EMPLOYEE where empId='0001';

Indexes

1. CREATE INDEX

  CREATE INDEX index_name on table_name(column_name);

To Create Unique index:

  CREATE UNIQUE INDEX index_name on table_name(column_name);

2. DROP INDEX

DROP INDEX index_name ON table_name;

Views

1. Create a View

Creating a View:
CREATE VIEW View_name AS 
Query;

2. How to call view

SELECT * FROM View_name;

3. Altering a View

ALTER View View_name AS 
Query;

4. Deleting a View

DROP VIEW View_name;

Triggers

1. Create a Trigger

CREATE TRIGGER trigger_name trigger_time trigger_event
    ON tbl_name FOR EACH ROW [trigger_order] trigger_body
/* where
trigger_time: { BEFORE | AFTER }
trigger_event: { INSERT | UPDATE | DELETE }
trigger_order: { FOLLOWS | PRECEDES } */

2. Drop a Trigger

DROP TRIGGER [IF EXISTS] trigger_name;

Stored Procedures

1. Create a Stored Procedure

CREATE PROCEDURE sp_name(p1 datatype)
BEGIN
/*Stored procedure code*/
END;

2. How to call Stored procedure

CALL sp_name;

3. How to delete stored procedure

DROP PROCEDURE sp_name;

Joins

1. INNER JOIN

SELECT * FROM TABLE1 INNER JOIN TABLE2 where condition;

2. LEFT JOIN

SELECT * FROM TABLE1 LEFT JOIN TABLE2 ON condition;

3. RIGHT JOIN

SELECT * FROM TABLE1 RIGHT JOIN TABLE2 ON condition;

4. CROSS JOIN

SELECT select_list from TABLE1 CROSS JOIN TABLE2;