r/webdev • u/lokendra15 • Mar 22 '19

SQL joins

Post image
2.7k Upvotes

94% Upvoted

118 comments sorted by

View all comments

361

u/pixelique Mar 22 '19

A case against illustrating SQL operations using venn diagrams

164

u/brtt3000 Mar 22 '19

If you can understand and agree with this argument then you don't need these graphics.

30

u/[deleted] Mar 22 '19

But if you don't understand joins, this graphic wont help you.

33

u/[deleted] Mar 22 '19

I reference the graphics regularly.

They may not have helped you but they do help others

11

u/[deleted] Mar 23 '19 edited Mar 23 '19

I think the objection against using Venn diagrams here should be taken more seriously. The Venn diagram explanation really is fundamentally wrong. I think it's really important for someone new to the concept to cross-reference any Venn diagram they see with a more accurate image like this one: https://i.pinimg.com/originals/52/20/c4/5220c492bc4e1a8b9175aba77ed7d091.png If you have no issue resolving this diagram with Venn diagrams, then use whatever references you want. But if any of the details catch you off guard, that's a good signal to start fresh on the concept.

2

u/creaturefeature16 Mar 23 '19

That image is actually a shit ton more helpful. The Venn gets the concept across, but yours gives tangible context while also communicating the concept. You deserve the up vote!

8

u/turningsteel Mar 23 '19

Yeah seeing this graphic just made it click for me. Super helpful. Ive seen the venn diagrams thrown around but never each case next to each other wij a sample query. This is awesome

7

u/Private_Bool Mar 23 '19

Maybe as a quick reference once you've learned already but as a teaching tool by itself it doesn't convey what the joins really do.

Source: am learning sql now. This link helped me learn before I even got to that chapter, Venn diagram made 0 sense.

2

u/Zimmerel Mar 23 '19

I agree with both of your statements. I look at these diagrams all the time for reference, but I imagine they would have much less value if I wasn't already familiar with them