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sqlclarify
Yak Posting Veteran
56 Posts |
 Posted - 2008-10-17 : 01:25:54
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| I have 4 tables.A, B, C, and E which have been joined via their keys.I want to join another table Q to these joined tables. But according to the keys I can join Q to B, C, or E. How do I decide whether to join Q to B, C, or E? |
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Jawad Khan
Starting Member
21 Posts |
Posted - 2008-10-17 : 02:22:49
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| This is totally a matter of design and business rules. Which table to join, depends upon the scenario you are working in. |
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rammohan
Posting Yak Master
212 Posts |
Posted - 2008-10-17 : 02:52:39
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| Its all depends on your rules of u r project. but take care about forming loops when u r joining tables like a->b->c->aOne can never consent to creep,when one feels an impulse to soarRAMMOHAN |
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mmqsql
Starting Member
2 Posts |
Posted - 2008-10-17 : 22:17:36
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| could you please give me a minor example about how it depends on rules?Thank you! |
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ForkandBeard
Starting Member
10 Posts |
Posted - 2008-10-18 : 07:23:30
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| Like all have said. You really need to give us more details but sometimes, where multiple joins are valid, starting with the table with the fewest results doesn't hurt, as it may improve efficiency.Many ThanksMitchellwww.forkandbeard.co.uk |
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malaytech2008
Yak Posting Veteran
95 Posts |
Posted - 2008-10-18 : 13:07:24
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| As all said, first four tables u joined using keys.Fifth table u can join directly to Q from any of the three table.It does not make difference, if Q contains records having one-to-one relationship with other three table.Otherwise u make ur choice according to B rules.ThanksMalaymalay |
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sqlclarify
Yak Posting Veteran
56 Posts |
Posted - 2008-11-07 : 01:15:54
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| Can you lead me to an article online or a book or something which would demonstrate this and explain this to me please?(P.S. I did try searching online, could not find anything which answers my question, the reason why I asked) |
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visakh16
Very Important crosS Applying yaK Herder
52326 Posts |
Posted - 2008-11-07 : 01:42:04
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| see this. quite a lot of articles on joinshttp://weblogs.sqlteam.com/jeffs/category/248.aspx |
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joins?