MySQL: FOREIGN KEYS are easy (kind of)

#MySQL #course #tutorial

00:00:00 intro
00:00:50 CREATE TABLE customers
00:01:17 INSERT INTO customers
00:01:58 CREATE TABLE transactions w/ FOREIGN KEY
00:02:20 Add FOREIGN KEY to a new table
00:03:34 DROP FOREIGN KEY
00:04:07 ADD a named FOREIGN KEY to an existing table
00:05:28 re-populating our transactions table
00:05:45 AUTO_INCREMENT transactions
00:06:05 inserting new rows into transactions
00:07:21 attempting to delete a referenced primary key
00:07:53 conclusion

CREATE TABLE customers (
customer_id INT PRIMARY KEY AUTO_INCREMENT,
first_name VARCHAR(50),
last_name VARCHAR(50)
);
INSERT INTO customers (first_name, last_name)
VALUES ("Fred", "Fish"),
("Larry", "Lobster"),
("Bubble", "Bass");
SELECT * FROM customers;

-- Add a named foreign key constraint to a new table
CREATE TABLE transactions (
transaction_id INT PRIMARY KEY AUTO_INCREMENT,
amount DECIMAL(5, 2),
customer_id INT,
FOREIGN KEY (customer_id) REFERENCES customers(customer_id)
);
ALTER TABLE transactions
AUTO_INCREMENT = 1000;

-- Add a named foreign key constraint to an existing table
ALTER TABLE customers
ADD CONSTRAINT fk_customer_id
FOREIGN KEY (customer_id) REFERENCES customers(customer_id);

[BroCodez]

CREATE TABLE customers (
customer_id INT PRIMARY KEY AUTO_INCREMENT,
first_name VARCHAR(50),
last_name VARCHAR(50)
);
INSERT INTO customers (first_name, last_name)
VALUES ("Fred", "Fish"),
("Larry", "Lobster"),
("Bubble", "Bass");
SELECT * FROM customers;

-- Add a named foreign key constraint to a new table
CREATE TABLE transactions (
transaction_id INT PRIMARY KEY AUTO_INCREMENT,
amount DECIMAL(5, 2),
customer_id INT,
FOREIGN KEY (customer_id) REFERENCES customers(customer_id)
);
ALTER TABLE transactions
AUTO_INCREMENT = 1000;

-- Add a named foreign key constraint to an existing table
ALTER TABLE customers
ADD CONSTRAINT fk_customer_id
FOREIGN KEY (customer_id) REFERENCES customers(customer_id);

[red_uwu]

Weeks of classes condensed into just a few videos, thank you for making this!

[pdalmao]

This has saved my life! Managed to get my module done with weeks to spare thanks to you :)

[maraki_zrg]

bro why u always have the BEST tutorials out there and as much as i search the whole yt i always end up warching YOUR vids?😂 keep up the good work man all of us IT students appreciate it. you are far better than our professors

[fgbeast]

You are the best! You make a difference on this world!

[TheLastRaven]

Litarly covered this in class yesterday tnx Bro! Your timing is as always great

[mehmetoz]

I am preparing for an interview. The explanation was simple and included good examples.

[bekirs]

I rarely need these kinds of videos but i still click and give a like just cuz ur a good guy and teacher

[gopinath]

so clean and neet and explained perfectly

[babajideamure]

@brocode I am late to the party. This is hands down the best video I have watched to explain PK and FK. Thank you

[ArielLegoAndMore]

Bro your tutorials are better than my sql teacher, you probly saved my test and also made me appreciate sql way more, much thanks!

[markvilla]

I am not IT student. I am lucky I found your channel :)

[sominramchiary]

unique key is easy, auto_increment is awesome and foreign_keys are easy (kind of), HUh!! Bro made it easy.

[fahriekurniadi]

thank you so much, help me to understand

[mithunchandrasaha]

Very Nice Explanation, Sir.Needs More.

[celestepozzi]

i like ur videos short and unique style of teaching, very easy to get, specially my main language is not english

[bexacode]

I really like all your videos!
And I really want you will upload about Spring Framework. 😇

[SchSlendy]

"im going to delete some of our customers" made me laugh xd. this tutorial is very cool, good work bro!

[bartsworkshop]

Thank you, you made this super easy to understand! One question, would the foreign key ever be a primary key as well in the transactions table?

[loebys]

nice video, easy to understand. May Allah increase your knowledge and be blessed with knowledge