DB: How to draw a precedence graph (rules + 3 examples)

You have indeed no global cycle of all transactions. But you have a cycle in T1,T2. You could indeed say, that {T1, T2} (as one entity) and {T3} is conflict serializable.
Though, in this example I don't look at it in that way. My statement of "conflict serializable" / "not conflict serializable" refers to all transaction. So I mean "all transaction are conflict serializable" or "all transactions are not conflict serializable".
If you're concerned about exams, you should ask your teacher in which way he wants the statement to be.

Comment from TNH91 (didn't verify this content yet):
"If two different transactions contain at least one write and one (read/write) on the same field, then draw an arrow from the earlier to the later."

Video erstellt mit HyperCam2

[mienislav]

You explained 80% of required transaction knowledge for my retake in less than 8 minutes while my teacher was only reading slides and required us to draw these graphs without explaining a bit. Thank you so much! I hope I will pass tomorrow!

[TNH]

This was a bit clearer to me than the wikipedia entry on the same thing. Mostly because the explanation on Wikipedia is a bit convoluted, but the drawing of the arrows straight onto the visualised stories was an excellent aid as well. More succinctly: If two different transactions contain at least one write and one (read/write) on the same field, then draw an arrow from the earlier to the later.

[kelonyofficialyn_baby]

Thanks for your crystal clear explanation. You saved my life

[mathoesify]

You made this concept so clear and easy to understand for me . THANK YOU!

[clover]

this was condensed and so clear so on point. Perfect.

[pifmu]

the simpliest and the best explaination of the youtube

[roninbrookes]

Thank you Thank you Thank you Thank you Thank you Thank you Thank you BLESS YOU SIR

[phongtrangia]

Man, thank you so much, just for some mins I already get it, the way you teach help me a lot, thanks

[AyushKumar-gfth]

Thank you. Simplest and best Explanation.

[PinkBlanketofficial]

Thanks a ton tomorrow I have my exam thanks a

[domi]

5:03 why didn't you take T1: W(B) and T3:W(B) as a conflict. It's on the same object, it's a Write and it's different transactions. Am I missing something?

[stargazing]

Thank u so much. You explained so well so effortlessly understood! great job!

[AdiNagara]

Hello, I would like clarify something in the third example you gave... It seems to me that there is no cycle in the graph, therefore the transactions are in fact conflict serializable. In any case, thank you for sharing!

[sherrywinfield]

Man! This is awesome! Thanks! Better than my prof... is there any more? About Xact and especially QEval?

[shubhamgulekar]

Thanks a lot for this short and wonderful explanation ❤

[Akonitx]

AWesome bro, awesome. Thanks that you exist!

[elvan]

Please post more videos like this covering other related subjects. This is way better than my lecturers explanation

[Aedu-uxsj]

Got more clear idea about precedence graphs.thank you

[ahmet]

Can we say, at 5:50, not conflict serializable, if the T1 to T2 reversed? say if the arrow direction is from T2 to T1?

[meenakshisamg]

In second example at 4:12 we need not to connect t1 read(a) To t2 write(a) as t1 has committed before this write yet the transaction is conflict serializable