Getting Started with MySQL
Basics
MySQL Locations
- Mac:
/usr/local/mysql/bin - Windows:
C:\Program Files\MySQL\MySQL _version\bin - Xampp:
/xampp/mysql/bin
Add mysql to your PATH
Mac/Linux:
# Current Session
export PATH=${PATH}:/usr/local/mysql/bin
# Permanantly
echo 'export PATH="/usr/local/mysql/bin:$PATH"' >> ~/.bash_profile
Windows:
- Find the path that contains
mysql.exe, it should be something likeC:\Program Files\MySQL\MySQL Server 5.6\bin. - Then add that path to path variable in system variables of Environment variables.
User Management
Login
mysql -u root -p
Show Users
SELECT User, Host FROM mysql.user;
Create User
CREATE USER 'someuser'@'localhost' IDENTIFIED BY 'somepassword';
Grant All Priveleges On All Databases
GRANT ALL PRIVILEGES ON * . * TO 'someuser'@'localhost';
FLUSH PRIVILEGES;
Show Grants
SHOW GRANTS FOR 'someuser'@'localhost';
Remove Grants
REVOKE ALL PRIVILEGES, GRANT OPTION FROM 'someuser'@'localhost';
Delete User
DROP USER 'someuser'@'localhost';
Exit
exit;
Databases
Show Databases
SHOW DATABASES
Create Database
CREATE DATABASE test_db;
Delete Database
DROP DATABASE test_db;
Select Database
USE test_db;
Tables
Show all Tables in Current Database
SHOW TABLES;
Create Table
CREATE TABLE users(
id INT AUTO_INCREMENT,
first_name VARCHAR(100),
last_name VARCHAR(100),
email VARCHAR(50),
password VARCHAR(20),
location VARCHAR(100),
dept VARCHAR(100),
is_admin TINYINT(1),
register_date DATETIME,
PRIMARY KEY(id)
);
Delete / Drop Table
DROP TABLE tablename;
Show Columns of a Table
DESCRIBE table_name;
Show the information of a column in a table
DESCRIBE table_name column_name;
Add New Column
ALTER TABLE users ADD age VARCHAR(3);
Modify Column
ALTER TABLE users MODIFY COLUMN age INT(3);
Add Primary Key into Table
ALTER TABLE table_name
ADD PRIMARY KEY (column_name,...);
Remove the primary key of a table
ALTER TABLE table_name
DROP PRIMARY KEY;
Row & Columns
Insert Row / Record
INSERT INTO users (first_name, last_name, email, password, location, dept, is_admin, register_date) values ('Brad', 'Traversy', 'brad@gmail.com', '123456','Massachusetts', 'development', 1, now());
Insert Multiple Rows
INSERT INTO users (first_name, last_name, email, password, location, dept, is_admin, register_date) values ('Fred', 'Smith', 'fred@gmail.com', '123456', 'New York', 'design', 0, now()), ('Sara', 'Watson', 'sara@gmail.com', '123456', 'New York', 'design', 0, now()),('Will', 'Jackson', 'will@yahoo.com', '123456', 'Rhode Island', 'development', 1, now()),('Paula', 'Johnson', 'paula@yahoo.com', '123456', 'Massachusetts', 'sales', 0, now()),('Tom', 'Spears', 'tom@yahoo.com', '123456', 'Massachusetts', 'sales', 0, now());
Select
SELECT * FROM users;
SELECT first_name, last_name FROM users;
Where Clause
SELECT * FROM users WHERE location='Massachusetts';
SELECT * FROM users WHERE location='Massachusetts' AND dept='sales';
SELECT * FROM users WHERE is_admin = 1;
SELECT * FROM users WHERE is_admin > 0;
Delete Row
DELETE FROM users WHERE id = 6;
Update Row
UPDATE users SET email = 'freddy@gmail.com' WHERE id = 2;
Data Ordering & Aggregating
Order By (Sort)
SELECT * FROM users ORDER BY last_name ASC;
SELECT * FROM users ORDER BY last_name DESC;
Select Distinct Rows
SELECT DISTINCT location FROM users;
Aggregate Functions
SELECT COUNT(id) FROM users;
SELECT MAX(age) FROM users;
SELECT MIN(age) FROM users;
SELECT SUM(age) FROM users;
SELECT UCASE(first_name), LCASE(last_name) FROM users;
Group By
SELECT age, COUNT(age) FROM users GROUP BY age;
SELECT age, COUNT(age) FROM users WHERE age > 20 GROUP BY age;
SELECT age, COUNT(age) FROM users GROUP BY age HAVING count(age) >=2;
Concatenate Columns
SELECT CONCAT(first_name, ' ', last_name) AS 'Name', dept FROM users;
Data Searching
Between (Select Range)
SELECT * FROM users WHERE age BETWEEN 20 AND 25;
Like (Searching)
SELECT * FROM users WHERE dept LIKE 'd%';
SELECT * FROM users WHERE dept LIKE 'dev%';
SELECT * FROM users WHERE dept LIKE '%t';
SELECT * FROM users WHERE dept LIKE '%e%';
Not Like
SELECT * FROM users WHERE dept NOT LIKE 'd%';
IN
SELECT * FROM users WHERE dept IN ('design', 'sales');
Foreign Keys & Joins
Create & Remove Index
CREATE INDEX LIndex On users(location);
DROP INDEX LIndex ON users;
New Table With Foreign Key (Posts)
CREATE TABLE posts(
id INT AUTO_INCREMENT,
user_id INT,
title VARCHAR(100),
body TEXT,
publish_date DATETIME DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY(id),
FOREIGN KEY (user_id) REFERENCES users(id)
);
Add Data to Posts Table
INSERT INTO posts(user_id, title, body) VALUES (1, 'Post One', 'This is post one'),(3, 'Post Two', 'This is post two'),(1, 'Post Three', 'This is post three'),(2, 'Post Four', 'This is post four'),(5, 'Post Five', 'This is post five'),(4, 'Post Six', 'This is post six'),(2, 'Post Seven', 'This is post seven'),(1, 'Post Eight', 'This is post eight'),(3, 'Post Nine', 'This is post none'),(4, 'Post Ten', 'This is post ten');
INNER JOIN
SELECT
users.first_name,
users.last_name,
posts.title,
posts.publish_date
FROM users
INNER JOIN posts
ON users.id = posts.user_id
ORDER BY posts.title;
New Table With 2 Foriegn Keys
CREATE TABLE comments(
id INT AUTO_INCREMENT,
post_id INT,
user_id INT,
body TEXT,
publish_date DATETIME DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY(id),
FOREIGN KEY(user_id) references users(id),
FOREIGN KEY(post_id) references posts(id)
);
Add Data to Comments Table
INSERT INTO comments(post_id, user_id, body) VALUES (1, 3, 'This is comment one'),(2, 1, 'This is comment two'),(5, 3, 'This is comment three'),(2, 4, 'This is comment four'),(1, 2, 'This is comment five'),(3, 1, 'This is comment six'),(3, 2, 'This is comment six'),(5, 4, 'This is comment seven'),(2, 3, 'This is comment seven');
Left Join
SELECT
comments.body,
posts.title
FROM comments
LEFT JOIN posts ON posts.id = comments.post_id
ORDER BY posts.title;
Join Multiple Tables
SELECT
comments.body,
posts.title,
users.first_name,
users.last_name
FROM comments
INNER JOIN posts on posts.id = comments.post_id
INNER JOIN users on users.id = comments.user_id
ORDER BY posts.title;