MySQL: FOREIGN KEYS are easy (kind of)

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  • Опубліковано 5 жов 2024

КОМЕНТАРІ • 60

  • @BroCodez
    @BroCodez  Рік тому +47

    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);

    • @ahmedhussein6359
      @ahmedhussein6359 Рік тому +2

      two typo errors:
      -- Add a named foreign key constraint to a new table //TYPO ERROR 1: should be unnamed
      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 //TYPO ERROR 2: should be transactions
      ADD CONSTRAINT fk_customer_id
      FOREIGN KEY (customer_id) REFERENCES customers(customer_id)

  • @red_uwu
    @red_uwu Рік тому +56

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

  • @maraki_zrg
    @maraki_zrg Рік тому +18

    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

    • @vishalplayzz2580
      @vishalplayzz2580 Рік тому +1

      true

    • @FunTubexArabic
      @FunTubexArabic 4 місяці тому +1

      True I share that point I even learned English to understand Him 😂😂 if I stay At home watching his videos I see much better than going to school wasting time and make my life miserable

  • @pdalmao
    @pdalmao Рік тому +6

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

  • @ArielLegoAndMore
    @ArielLegoAndMore Рік тому +8

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

    • @FunTubexArabic
      @FunTubexArabic 4 місяці тому

      The point is that he Took A serious lesson to funny story So hilarious 😂😂

  • @TheLastRaven
    @TheLastRaven Рік тому +5

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

  • @markvilla7796
    @markvilla7796 11 місяців тому +3

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

  • @fgbeast5805
    @fgbeast5805 Рік тому +1

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

  • @mehmetoz886
    @mehmetoz886 8 місяців тому

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

  • @bekirs4240
    @bekirs4240 Рік тому +1

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

  • @sominramchiary5880
    @sominramchiary5880 3 місяці тому

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

  • @loebys
    @loebys Рік тому +1

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

  • @gopinath9986
    @gopinath9986 3 місяці тому

    so clean and neet and explained perfectly

  • @celestepozzi9204
    @celestepozzi9204 Рік тому

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

  • @babajideamure108
    @babajideamure108 Рік тому

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

  • @bartsworkshop
    @bartsworkshop Рік тому +2

    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?

  • @maaboii5431
    @maaboii5431 Рік тому

    Really frustrated till now trying to learn how primary key work.
    I have no idea how to insert multiple same column data (the assigment the gave me) meanwhile primary key doesn't work if you add duplicate data, besides that problem i pretty much know well how to use mySQL, thanks to this video ofc

  • @mithunchandrasaha403
    @mithunchandrasaha403 Рік тому

    Very Nice Explanation,Sir.Needs More.

  • @tomh6010
    @tomh6010 Рік тому +4

    Great video! Any plans on covering relational databasing? That's probably the next thing that stumps a lot of people imo
    Also huge respect for the fundraiser, it's a great cause :)

  • @bexacode1150
    @bexacode1150 Рік тому

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

  • @jubibi390
    @jubibi390 10 місяців тому

    This saved me. I love you Bro.

  • @SchSlendy
    @SchSlendy 2 місяці тому

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

  • @fahriekurniadi403
    @fahriekurniadi403 Рік тому

    thank you so much, help me to understand

  • @sandyiwadeakhia4435
    @sandyiwadeakhia4435 2 місяці тому

    Please,I need video on how to create multiple tables on postgreSQL.....

  • @drawdownfx4415
    @drawdownfx4415 5 місяців тому

    this is great thanks. To do joins between two tables do we need to specifiy primary and foreign keys? What if you have two tables with no constraints? would it still be possible to do join queries

  • @wolfdogfifa
    @wolfdogfifa 19 днів тому

    Is there a way to display the first name of the customer in the transactions table by using the customer_id as the foreign key? Or would you have to make the first name the foreign key to display it in the table?

  • @meitangyoon7087
    @meitangyoon7087 Рік тому

    Great lessons - as a beginner, it's short & sweet makes it easy to follow & understand. Seen other youtube lessons - difficult to follow for beginners. The comments pinned by you are very helful guide & notes. Great job, kudos to you and look forward for more.

  • @samitee8336
    @samitee8336 Рік тому

    The typing sound is so satisfying😅

  • @mr_clean575
    @mr_clean575 Рік тому

    Thank you so much!!!

  • @Lifeofrandomness
    @Lifeofrandomness Рік тому

    Thanks a ton Man!

  • @boogieman8827
    @boogieman8827 Рік тому +1

    Can we put a foreign key in a constraint. Like table_1 has column_D.O.B as primary key and table_2 has column_joining_date and joining_date should be greater than D.O.B .
    How do we do that?

  • @luckycreative7418
    @luckycreative7418 Рік тому +1

    I HAVE A QUESTION WHY YOU HAVE DROPPED THE TABLE?
    PLS CAN SOMEONE RESPOND!!!!

    • @freezeyourmind7011
      @freezeyourmind7011 Рік тому

      I don't understand it too, he deleted table but still can link and use it

  • @mukhtarabebefe7596
    @mukhtarabebefe7596 Рік тому

    Thank you

  • @lorenne928
    @lorenne928 11 місяців тому

    very great

  • @enriquepasa
    @enriquepasa Рік тому

    Cool video bro :) better than going through theoretical crap - straight to action

  • @aatifmohammed7031
    @aatifmohammed7031 Рік тому +1

    how to make foreign key on non primary columns?

    • @maxxcleiton
      @maxxcleiton 4 місяці тому

      FOREIGN KEY is a PRIMARY KEY from another table.
      The definition by itself answers your question.

  • @korosai
    @korosai 7 місяців тому

    why you use transaction_id as a primary key if we don’t pair it with a foreign key?

  • @ToughNevyHacSoc
    @ToughNevyHacSoc Рік тому +1

    Hey Bro Code, Can you please please help me with creating a draw method in a tick-tak-toe game you created your-self, I really want that, and I've been trying for weeks, but I could not figure any way out. Please if you know how to create one, replay in my comment.

  • @NerdyGeecks
    @NerdyGeecks 4 місяці тому

    hello, can someone explain on how to insert an existing foreign key into two tables like inserting user_id and two tables like transaction and reserve in phpmyadmin?

  • @luffy_viz
    @luffy_viz 4 місяці тому

    I see last that line delete form table name and where name = ' vishwa ' ; but I can't delete then how to delete in 2 tables

  • @MathewGKuzhivelil
    @MathewGKuzhivelil Рік тому

    What if I have 3 tables and the 2 nd table has a dk with 3 rd table and vice-versa and it shows error while execution.

  • @sandyiwadeakhia4435
    @sandyiwadeakhia4435 2 місяці тому

    How do i create two foreign keys in a table?

  • @suryatejamukka5564
    @suryatejamukka5564 2 місяці тому

    Error Code: 1822. Failed to add the foreign key constraint. Missing index for constraint 'idx_product_name' in the referenced table 'products'
    What is this how to solve this

  • @xelozzen5312
    @xelozzen5312 Рік тому

    why is mine key.. doesn't exist in table i write it exact like yours tho

  • @vishalmane3139
    @vishalmane3139 Рік тому

    didnt work..column missing

  • @ambi297
    @ambi297 4 місяці тому

    in my sql the data is not taking it says cannot foreign key constraints unable to different tyoes alo what shell i do????

    • @aetyrunner
      @aetyrunner 4 місяці тому

      Pk and FK must have same data type, like INT/SMALLINT/etc are all INT, but not like INT-DECIMAL or INT-VARCHAR
      Then if your PK is SMALLINT (one of most common cases I guess) your FK should be:
      column_id INT,
      FOREING KEY(column_id) REFERENCES table(column_id)

  • @amroulouay6819
    @amroulouay6819 Рік тому +1

    Why the unique name should be fk 😂😂4:17

  • @evanlin7656
    @evanlin7656 2 місяці тому

    i like Bubble bass

  • @f15srinivas82
    @f15srinivas82 5 місяців тому

    i didnt see god . even i didnt see you bro

  • @dlamontw
    @dlamontw 6 місяців тому

    nice ok. i think i got it

  • @AZZAMNO1
    @AZZAMNO1 9 місяців тому

    maybe this will be useful for someone in future i'll drop this here.
    ALTER TABLE student
    ADD COLUMN student_loginUsername VARCHAR(35),
    ADD FOREIGN KEY (student_loginUsername) REFERENCES login(login_username);