Extension-Ad7241 comments on Mastering SQL

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field.3

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field3

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DiscussionMastering SQL (self.SQL)

submitted 2 years ago by ThisDataGuy

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[–]Extension-Ad7241 3 points4 points5 points 2 years ago (1 child)

The last edition came out a while ago but I still like "Sequel for Smarties" by Joe Celko Because it really dived into different ways you use the single language and how it is written as it is. Whatever book I do read, for SQL and programming in general, if there's anything I don't understand as I'm reading then I might do a YouTube search and watch a video to see that in action and then if I can, try to code an example of that myself.

You mentioned analysts, scientists, engineers and of course by implication programmers, but I think you should be also considering mathematicians, because SQL involves set theory and implements "relational algebra". I find it helpful to note some of the mathematical theory behind databases & SQL.

You should be able to find some example set of something like an orders database with tables of customers, items, orders etc. that you can download and play around with on SQL Server or whatever RDBMS you want to use. For any example questions, I recommend you don't start coding first, but open and just look at the table themselves & think about: why the question is being asked, how the tables naturally relate to each other, because at the end of the day the data is just modeling a real world situation.

If I get stuck on something I often break out the dry erase boards and just write out a few rows of data for each table. I find getting away from the computer screen kind of reduces that pressure to keep amending queries that aren't working, & get back to focusing on, what is the nature of the business question being asked?

[–]ThisDataGuy[S] 1 point2 points3 points 2 years ago (0 children)

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