Database Design 29 - Foreign Key Constraints

[@briddenattech]

"Sorry if I talk fast." Bud, I've been listening to you at 2x. Talk as fast as you want. Give me a challenge.

[@jacobcasey28]

One of the best things about self-studying is coming across cool dudes like this who can explain things in a good way, thanks!

[@codebreakthrough]

Learn about Foreign Key Constraints by clicking below. Make sure you watch the other videos in the series! buff.ly/1uqxUf6

[@weatherlye71]

I not only learned some essential things here that allowed me to understand the schema of a programmer I know, but it makes me feel like you are my older grandson! You are brilliant AND adorable. Thank you. Also, I could not understand why fields in Infinium were being changed by SQL while working in a contract position. Now I realize the programmer probably was not aware that all these things are BUILT INTO Infinium and don't need to be updated, deleted or inserted by SQL. That approach is very illogical but it makes me appreciate IBM application SO MUCH. I don't hate SQL or Microsoft but it increased my appreciation of the iSeries (old AS400) systems and applications they support.

[@amynash1999]

one of the better videos on database.

[@sherlock4209]

Thank you man. Amazing explanations and easy to understand!

[@basementhermit3607]

Excellent explanation, very easy to understand. Thanks a lot for uploading this video.

[@joelkeane8740]

Awesome video mate! Really well explained - thanks : )

[@alexdan111111111111]

Great! I have never found yet such a great explanation on other tutorials... ON DELETE/ON UPDATE ... RESTRICT/CASCADE/SET NULL. ON DELETE SET NULL... that fantastic. You can delete the parent, but not the childeren...

[@minhtao9774]

"Get away stupid fly!" Hahahaha! Best part of this video =] and everything else hehe!

[@kayoutube690]

Question, is there any conflict to FK constrain once i am going to backup the table which associated to the FK?

[@pearlipop]

Your teaching is great Caleb, thank you for your videos! I have a question, is your goal to be a teacher? Or are you one, already?

[@codebreakthrough]

***** I am! ...on KZbin. hehehehe

[@joshfraser3991]

pearlipop is right you are good! I am going to follow you!

[@liangwu8328]

In what book I can learn these database concepts? Do you have any recommendations?

[@canberkuyar5469]

thx buddy it was so helpful you teach really well ^^

[@JoshuaMusau]

well explained. thanks

[@aw18473]

Well explained 👍👍👍👍

[@grafitechdesigns6312]

great job bro, do you have videos on selection of tuple, projection operator, Cartesian product?

[@somachicasincity4232]

Thank you again this was helpful!

[@manjuelaiya8597]

i need answer for this question To ensure that the amount withdrawn shoulb be less then the credit card limit amount , to ensure integrity what type constraint will be use ? a. column level check constraint b.table level foreign constraint c.table level level check constraint d.column level foriegn key constraint

[@dnj20]

thumbs up. t'es vraiment bon

[@varunjain3756]

well explained Foreign Key Constraints

[@anishkuber764]

Thanks man

[@eluented]

thanks man life saver

[@amalsakkoumi1392]

Thanks from morocco

[@robertoquinones785]

Great DUDE!!! Thanks

[@amritkaur2142]

u r awsome

[@soultouchingsongs]

Excellent. Thanks a ton!

[@hunterblake2710]

Good explanation

[@sierrakilo9695]

So how WOULD you keep comments if a user deletes their account?

[@cjlion7081]

an update to set all comments by user x to null in the child table with the comments by users, select pk * inner join select fk from comments table where user = x

[@TheSkepticSkwerl]

Reddit shows the comments forever, unless the comment is deleted. It just updates the user to [deleted]... I wonder if they set null, or some other set like 'set = 0' and any comment with 0 or null (whatever they do) is the user [deleted] However, i think if you restore your account, it restores the comment owner. They're good

[@davidflash1]

thanks, regards

[@TheSkepticSkwerl]

504 - gcih. 508 - gcfa

[@guypicard1648]

Most of these constraints are based on the fact that you plan on changing the primary key in one of the tables - which you should never do. Foreign keys are important. But foreign key contraints? meh. Just make sure to never change the value of a primary key.

[@codebreakthrough]

Well foreign key constraints also ensure that the value of the foreign key field exists in the referenced column on insert. That way you you avoid orphaned rows

[@cjlion7081]

@@codebreakthrough which is what the fk constraint construct is for, if you choose to use it. It's not a normal thing to do clearly, but can be useful. His overview also helps people understand basic key and constraint interaction concepts, important to beginners

[@OneTimWhatley]

Your chalk is small.

[@kld0093]

noll

[@eldoprano]

gosh you are so handsome..

[@user-em9mw9ch3y]

People would love you in India. (hint : your surname)

[@manjuelaiya8597]

i need answer for this question To ensure that the amount withdrawn shoulb be less then the credit card limit amount , to ensure integrity what type constraint will be use ? a. column level check constraint b.table level foreign constraint c.table level level check constraint d.column level foriegn key constraint