Re: Which column is taken in JOIN with multiple columns and different content ?
- From: "William Robertson" <williamr2019@xxxxxxxxxxxxxx>
- Date: 3 Mar 2007 03:52:11 -0800
On Mar 3, 4:38 am, Digeratus 2006 <digeratus2...@xxxxxxxxxxxxxxxxxxxx>
wrote:
mer...@xxxxxxx (Tobias Merler) wrote innews:45e84bdf$0$23135$9b4e6d93@xxxxxxxxxxxxxxxxxxxxxxxxxxx:
Assume I join two tables.
Both of these tables contain a column with name "col1". This column
ist not he primary key. However this column contains different values
which value is taken ?
Lets see the following example:
Select *
FROM tablea a, tableb b
Where a.id = b.id
tablea:
id col1 col2
1 aaa ddd
2 bbb eee
3 ccc fff
tableb:
id col1 col3
1 zzz uuu
2 xxx vvv
3 yyy www
The result table will look like:
id col1 col2 col3
1 ??? ddd uuu
2 ??? eee vvv
3 ??? fff www
Which values will be for the questions marks ?
Ok, I know the data model is not perfect and the two tables could be
merged. But keep in mind that the sample is only a simplified version
of a more complex SQL statement. So lets concentrate on my question.
Thank you
Toby
Toby,
Because of the conflicting column names, Oracle would give you a syntax
error, try it. The syntax in Oracle would be select a.*, b.*. The
resulting table should be apparent now.
Andy Young
I'm nore puzzled about why anyone would think there might be a
problem. Would you also predict an error from this?
SQL> select deptno, dname, dname from dept;
Perhaps you are thinking of the error you get when a column is
ambiguously defined in a subquery and you then refer to it in the
outer query.
.
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