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smile
Starting Member
22 Posts |
 Posted - 2009-03-15 : 17:26:36
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| Hello again!Here's my question: let's say I have two tables - t1 and t2, and the query "select count(*) from t1 " returns 9, and "select count(*) from t2" returns 8. The why the query "select count(*) from t1,t2" returns 72? I see that the two results are multiplied but I don't get why...? So it does something like Cartesian product? |
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spirit1
Cybernetic Yak Master
11752 Posts |
Posted - 2009-03-15 : 18:02:07
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| yesselect count(*) from t1,t2creates a cross join between t1 and t2 which is the same as a cartesian product___________________________________________________________________________Causing trouble since 1980Blog: http://weblogs.sqlteam.com/mladenpSpeed up SSMS development: www.ssmstoolspack.com <- version 1.5 out! |
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smile
Starting Member
22 Posts |
Posted - 2009-03-15 : 18:14:07
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| Ok, thanks! |
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senthil_nagore
Master Smack Fu Yak Hacker
1007 Posts |
Posted - 2009-03-16 : 00:11:47
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| If you want the count as t1 by joining t2The query seems like Select count(a.*) from t1 a,t2 b where a.id=b.idRegardsSenthil.CWilling to update... |
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visakh16
Very Important crosS Applying yaK Herder
52326 Posts |
Posted - 2009-03-16 : 11:34:16
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| staring from sql 2005, you should busing new join syntax instead of below syntax as this wont be supported in future version of sql. |
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about "count"