Stairway to T-SQL DML Level 5: The Mathematics of SQL: Part 2

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Stairway to T-SQL DML Level 5: The Mathematics of SQL: Part 2

Greg Larsen

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November 30, 2011 at 12:00 am

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Comments posted to this topic are about the item Stairway to T-SQL DML Level 5: The Mathematics of SQL: Part 2
Gregory A. Larsen, MVP

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Fiacre Lenehan Mr or Mrs. 500 Points: 584 More actions · Answer 1

A very clear and informative article. A minor point is that the Figure numbers appear to be incorrect in the INNER Join Operator and OUTER JOIN Operator sections

Greg Larsen SSC-Insane Points: 20961 More actions · Answer 2

I reviewed the article text and your comment and I'm not following what part of the article has incorrect figure numbers. Would you please explain a little further so I can get the article corrected so it contains references to figures that a accurate.

Thank you

Greg

Gregory A. Larsen, MVP

Fiacre Lenehan Mr or Mrs. 500 Points: 584 More actions · Answer 3

"as shown in the Venn diagram in Figure 5" should this be Figure 3?

"INNER JOIN operation to return part 2 of Figure 6" should this be Figure 4?

Craig Thomson-419971 SSC-Addicted Points: 429 More actions · Answer 4

Thanks Gregory

It's always useful to review the basics.

I think a mathematical set regards any identical member as being the same thing, so in the diagrams there would only be one representative of any number.

I don't know where that leaves us with UNION ALL though, it seems to break the rules.

I'm happy to be corrected, I just scraped through my maths degree.

Craig

john.mcginley SSC Journeyman Points: 81 More actions · Answer 5

Very clear explanation of things we use daily and may never think about. Former Republican governor of Wisconsin Scott Walker should have read this a year ago.

steve.homer@gmail.com Grasshopper Points: 24 More actions · Answer 6

Thanks Gregory
It's always useful to review the basics.
I think a mathematical set regards any identical member as being the same thing, so in the diagrams there would only be one representative of any number.
I don't know where that leaves us with UNION ALL though, it seems to break the rules.
I'm happy to be corrected, I just scraped through my maths degree.
Craig

You're correct. Sets are defined as collections of unique elements. SQL however isn't set based, but rather based on bags (think Sets that allow duplicates).

See any of Chris Date's books for long rants about this 🙂

This reply was modified 5 years, 5 months ago by steve.homer@gmail.com.

mayoadams Newbie Points: 5 More actions · Answer 7

I think this is a very good way to teach essentials, using mathematical objects leached of the connotations of the "real world". Thank you.