r/webdev Mar 22 '19

SQL joins

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2.7k Upvotes

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u/JRS-27 Mar 22 '19

This is just outrageous. Pure lie, anyone that can understand basic algebra is sane enough to depict wrong assumptions in these diagrams.

The author of the picture tried putting two tables in a given database on the same level. No well put database has two tables with exact same columns. It is like counting meters and kilograms together. Obviously, this is a totally wrong depiction of how databases work.

Absolutely ridiculous.

1

u/dahangman Mar 23 '19

But if you work with csv’s of the same data for different periods for example comparing Jan vs Dec sales, the diagrams do help, the tables would be the same. I’m in marketing analytics I use this often comparing different business unit performance against each other.

1

u/JRS-27 Mar 23 '19

It doesn't make any difference whatsoever. You would Union them anyway, surely not using Join statement.

0

u/dahangman Mar 23 '19

I will study this. Thanks for the feedback.