-- Create Users Table
CREATE TABLE Users (
    user_id INT PRIMARY KEY,           -- Unique identifier for each user
    signup_date DATE NOT NULL           -- Date when the user signed up
);

-- Create Transactions Table
CREATE TABLE Transactions (
    transaction_id INT PRIMARY KEY,      -- Unique transaction identifier
    user_id INT,                         -- References Users table
    transaction_date DATE NOT NULL,      -- Date when the transaction occurred
    transaction_amount DECIMAL(10,2) NOT NULL,  -- Amount of the transaction
    CONSTRAINT fk_user FOREIGN KEY (user_id) REFERENCES Users(user_id) ON DELETE CASCADE
);

-- Insert data into Users table
INSERT INTO Users (user_id, signup_date) VALUES
(1, '2024-01-10'),
(2, '2024-02-15'),
(3, '2024-03-20'),
(4, '2024-04-05'),
(5, '2024-05-12');

-- Insert data into Transactions table
INSERT INTO Transactions (transaction_id, user_id, transaction_date, transaction_amount) VALUES
(101, 1, '2024-06-01', 100.00),
(102, 1, '2024-06-10', 200.50),
(103, 2, '2024-06-05', 150.75),
(104, 2, '2024-06-15', 300.00),
(105, 3, '2024-06-07', 500.25),
(106, 3, '2024-06-17', 250.00),
(107, 4, '2024-06-20', 400.00),
(108, 4, '2024-06-25', 100.00),
(109, 5, '2024-06-30', 50.00);  -- Only one transaction (should be excluded in the query)
by

MySQL online editor

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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;