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lici
Starting Member
11 Posts |
 Posted - 2005-02-07 : 15:45:07
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| Hi!!Somebady can tell me what is the difference between full join and union all?or, where i can find information about it?Tnx a lot |
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Xerxes
Aged Yak Warrior
666 Posts |
Posted - 2005-02-07 : 15:46:37
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| Books OnlineSemper fi, Xerxes, USMC (Ret) |
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Xerxes
Aged Yak Warrior
666 Posts |
Posted - 2005-02-07 : 15:50:08
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| First off, the difference between UNION and UNION ALL are simple: UNION eliminates duplicates. As for a 'FULL JOIN'....do you mean left outer or right outer?Semper fi, Xerxes, USMC (Ret) |
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tkizer
Almighty SQL Goddess
38200 Posts |
Posted - 2005-02-07 : 16:17:50
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Xerxes,Full outer join is different than left outer and right outer. Here's the description for full outer join:quote:
A full outer join returns all rows in both the left and right tables. Any time a row has no match in the other table, the select list columns from the other table contain null values. When there is a match between the tables, the entire result set row contains data values from the base tables.
Tara |
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jsmith8858
Dr. Cross Join
7423 Posts |
Posted - 2005-02-07 : 16:22:22
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| They are very different, but both can be used for similiar purposes. (i.e., to find unmatched rows in two tables in either direction) I recommend, personally, to use UNION ALL and to avoid FULL JOINS -- FULL JOINS (much like RIGHT JOINS) aren't very logically sound when designing a clearly defined SELECT statement.- Jeff |
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Xerxes
Aged Yak Warrior
666 Posts |
Posted - 2005-02-07 : 16:23:55
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| Tara & Jeff, Thanks again for clarifying. I personally like UNION ALLs, too.Semper fi, Xerxes, USMC (Ret) |
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Union All or Full Join?