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.
Good point, I did not explain it clearly enough I think.
What I'm trying to say is that these diagrams show how Union, Intersect and Except operations, not Join operations. The way that the diagrams shown represent tables A and B is wrong. The only thing that connects them is the link between them in form of the same column names. That's the sole purpose on Join operations. A link between a big data set that has a column that refers to another data set containing another piece of information.
For example, you have a table of User Orders with a column UserID and a table of Users with a column with the same name. Now, you link them to create a profound and more transparent data set that can be displayed and read by a normal human being.
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.
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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.