I spent close to 2-months trying to understand this topic from my studies. I spent 30mins with your video and I feel like I have gained relational algebra enlightenment. :) Thank you for doing up this video and teaching it so clearly!
thank u very much madame for an impressive tutorial, am now able to seat for my final db course exam at my college a million thanks once again may God bless u more more more and more......
Wow. These two videos were unbelievably helpful and easy to understand. In less than 40 minutes, you did a better job of covering what took my professor 5 one-hour lectures to cover. When I fill out my course evaluations, I'm going to link these videos. Hopefully my professor can learn from you on how to convey these concepts so efficiently.
These videos are great! In fact, I knew nothing on the subject, and the first video was so good, I actually caught the error she made at 3:58 before reading her correction shortly after. Great job!
When she does "pairs of colleges in same sate" with the first method, with the cross product, she selected s1 = s2, but don't you also have the Berkley Stanford and Stanford Berkley issue here as well as you did with the natural join?
Yup, she missed that i guess because it was not the final query that she was going to show, it also gets repetitions like "stanford stanford" "berkeley berkeley" i think
Time 4:00 Couldn't you just add a theta join instead of of a natural join with a project operator. Did you not do this because theta joins are rare? I thought you said otherwise when you explained it to us?
But what happens if you have more than 2 colleges that you are looking for pairs of ? She just used Berkeley and Stanford and assigned them to C1 and C2 what i there are 300 colleges do we have to list all of them like that ? (C1, C2...C50... C300)?
I didn't understand the concept of 'natural join' in the Difference operator. The SID is unique in all cases. It cannot be same. So why do we need a 'natural join' to remove duplicate values?
It doesnt allow you to do something you couldnt have done with the opertors introduced before. Its just an easier way to write something however you could have written it before aswell
Siyang Liang Someone correct me if I'm wrong, but you may have to look at previous lectures to understand. That question you are asking is actually not possible in this Student-Apply-School relation because I remember that the sID from the Apply table is the primary key. This means that a constraint of this whole relationship is that students can only apply once to a school.
Ste awoi I think the primary key for Apply is (sID, college, major). A student could apply multiple college. And a student could apply multiple majors for one college. Look at the original apply table.
10 years later and I can't still find a better RA explanation than this
You have just summed up a total of about 5 lectures which I slept through in these 2 parts videos. Thank you
+Iman Matar well said
Agreed
One person's clarity in a topic and the ability to transfer that knowledge can add to saving so many hours! Thank you for being so cogent.
who else has a databases exam tomorrow?
It might be 3 months later, but I do!
Today xD
6 days
it's today iiin about 3 hours :)
TheDruida72 today
You make me wonder how my professor is employed. Thank you for keeping this public.
I spent close to 2-months trying to understand this topic from my studies. I spent 30mins with your video and I feel like I have gained relational algebra enlightenment. :)
Thank you for doing up this video and teaching it so clearly!
Combination of Video 1 and 2, is awesome, I recommend anyone who wants learn relational algebra ...go through these
7 almost 8 years later, came upon these vids and...amazing stuff.
thank u very much madame for an impressive tutorial, am now able to seat for my final db course exam at my college a million thanks once again may God bless u more more more and more......
What a goddess. Learned more in 35 minutes than in a whole month at college. Amazing teacher.
In R, when you merge data frames, it employs the relational algebra paradigms mentioned in this video!
I want to appreciate how great this 2 videos were and how the professor explained the topic
Thank you professor for breaking this complex topic down. Obviously i have learnt within 40 minutes what i struggled to understand in weeks
I was soo lost on this subject before watching these two videos. This cleared it right up. Thank You!
I have found a gem in a time of online learning. Thank you!
i would like to thank you for this video tutorial series which consists short and sweet explanation in efficient way.
Wow. These two videos were unbelievably helpful and easy to understand. In less than 40 minutes, you did a better job of covering what took my professor 5 one-hour lectures to cover.
When I fill out my course evaluations, I'm going to link these videos. Hopefully my professor can learn from you on how to convey these concepts so efficiently.
this woman is a queen!!!
You explained this topic so simply. Thank you for posting these videos!
These videos are great! In fact, I knew nothing on the subject, and the first video was so good, I actually caught the error she made at 3:58 before reading her correction shortly after. Great job!
Thank you so much. I wish I would have watched these videos before mid term
"which is a standard set operation you learned about in elementary school" wtf elementary school did you go to?
Great video though, thanks a bunch!
When she does "pairs of colleges in same sate" with the first method, with the cross product, she selected s1 = s2, but don't you also have the Berkley Stanford and Stanford Berkley issue here as well as you did with the natural join?
Yup, she missed that i guess because it was not the final query that she was going to show, it also gets repetitions like "stanford stanford" "berkeley berkeley" i think
You could fix that by adding the condition n1 < n2 to the select operator. So the new condition would be s1 = s2 ^ n1 < n2.
@@abhinitsati3082 can you please explain how and why n1 < n2 would remove duplicates like Stanford, Berkley and Berkley, Stanford as shown @13:20?
At 13:41 when she uses n1
i think it compares the starting string that is B from Berkeley and S from Stanford.
i think it is alphabetical order
Exceptional teacher, thank you for the videos!
Thank you for writing the book we use for the course. Very informative
awesome explanation about important topic great work lady
the answer for the second difference example is wrong, @4:00, question asked for id & name but answer only gives name.
there's a little subtitle in red to correct the answer, hard to see though lol
No kidding, wasn't expecting it to be this easy
How does the less than work @ 13:25. How are you claiming a name of a school is less than another name of a school?
comes first alphabetically
All characters are ranked alphanumerically. Meaning that letters and numbers have a rank relative to each other.
Wait, SQL pronounced as "sequel"?
If you want it to
I pronounce it as Sakweeal for fun.
Do all database teachers just like having university structures as examples?
Time 4:00
Couldn't you just add a theta join instead of of a natural join with a project operator. Did you not do this because theta joins are rare? I thought you said otherwise when you explained it to us?
Brilliantly explained from india
very well explained , thank you
The division operator is missing?
thanks! these 2 videos help me a lot
I would pay money to have a professor teach me this content this well. Oh wait, I do :/
Finally, u made me realize that I wasted my money to those trash professors who takes away my 1 hour everyday taking shit.
great lecture today i`ve found how great lecturers are compared to those at my university :3
What's the link to the previous video? I searched through your videos and the naming system was insane.
Does anyone have the exercises to these lectures ? Thanks
what about the enrollment atribute? where does it say that it doesnt make it to the pairs?
But what happens if you have more than 2 colleges that you are looking for pairs of ? She just used Berkeley and Stanford and assigned them to C1 and C2 what i there are 300 colleges do we have to list all of them like that ? (C1, C2...C50... C300)?
The C1 and C2 is a cojoin of the two tables so it is only C1 and C2. the colleges within the table are what she represented with n1 and n2 i think
what if you want to find ids of student(s) that had the highest grade? How do you compare each student's grade?
I don't understand the meaning of "don't increase the expressive power of language." What does it mean??
Hope I'm not too late! It means you can write the exact same query with other operators.
I didn't understand the concept of 'natural join' in the Difference operator. The SID is unique in all cases. It cannot be same. So why do we need a 'natural join' to remove duplicate values?
It doesnt allow you to do something you couldnt have done with the opertors introduced before. Its just an easier way to write something however you could have written it before aswell
amazing video
ı understand thıs sectıon wıth the last example , thanks madam
Can somebody teach me how to write "get students who appliy multiple majors in one school"?
Siyang Liang Someone correct me if I'm wrong, but you may have to look at previous lectures to understand.
That question you are asking is actually not possible in this Student-Apply-School relation because
I remember that the sID from the Apply table is the primary key. This means that a constraint of this whole relationship is that students can only apply once to a school.
Ste awoi I think the primary key for Apply is (sID, college, major). A student could apply multiple college. And a student could apply multiple majors for one college. Look at the original apply table.
this is just great
good explanation
very helpful
Thank you,Very helpful
very nice
Thank you!
thank you so much ... :)
Thank you !!
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Hair color is changed
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Thank you!