April 22, 2013 at 6:42 am
Nice question, interesting discussion.
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April 23, 2013 at 6:16 am
WWDMark (4/18/2013)
Danny Ocean (4/17/2013)
kapil_kk (4/17/2013)
Nice question... learn something new today.. 🙂But can anyone plz explain me about the SUM part which is returning 12, I am not clear with this section :w00t:
Kapil, Cross join means Cartesian product. When query have multiple joins, it solve it from left to right. So first cross join take place between table #T1 and #T2. It gives 2 (1 *2) rows. Now these 2 rows have cross join with #T3. It gives 6 (2*3) rows. Output of this query look like below.
id1id2id3
111
112
113
121
122
123
Now calculate sum of column id3. its 1+2+3+1+2+3 = 12.
So Total row count is 6 and total of id3 column is 12.
I think this help you. 🙂
Thanks for the more in depth explanation, I was struggling to understand how we got 12 also!! Always learning! 😀
nice explanation... thanks for the question....
but where is the group by.....???? it is working without group by.....?????
Manik
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April 23, 2013 at 7:29 am
manik123 (4/23/2013)
but where is the group by.....???? it is working without group by.....?????
If the SELECT clause of a query contains ONLY aggregate functions, you can leave out the GROUP BY. The result will be a single row with the "grand total".
(I think everybody uses this in the basic form SELECT COUNT(*) FROM Table to get a count of rows from a table; the example here is a bit more complicated, but the same basic idea).
May 3, 2013 at 4:16 am
Another good question showing basics of joins. Thanks for this simple question with brilliant approach. +10
May 13, 2013 at 12:53 am
John Mitchell-245523 (4/18/2013)
Are the exclamation marks in the explanation an expression of surprise, or are they supposed to represent factorials?John
Yes, an unfortunate bit of punctuation.
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