Operator and condition precedence
- From: "Rich Jesse" <rjoralist@xxxxxxxxxxxxxxxxxxxxx>
- To: "Oracle L" <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 8 Sep 2009 15:49:39 -0500 (CDT)
Hey all,
A coworker asks me about casting an NCHAR column to NUMBER in a query on
10.1.0.5.0 (AIX), so I of course offer up the syntax of TO_NUMBER. Somewhat
knowing the data, I warn that conversions on columns of all spaces will
fail. But for some reason, this works:
select aa.stuff, bb.stuff
from table_a aa,
table_b bb
where aa.col_1a = bb.col_1b
and to_number(aa.col_2a) = bb.col_2b
and aa.col_3a = bb.col_3b
and aa.col_4b = bb.col_4b
and aa.col_6a in ('YY','ZZ')
and aa.col_2a > ' '
and aa.col_5a <> bb.col_5b;
Looking at the docs:
http://download.oracle.com/docs/cd/B14117_01/server.101/b10759/conditions001.htm#sthref874
...tells me that the above would attempt to convert an AA.COL_2A to a number
before filtering it out from the AA.COL_2A > ' ' part, but it obviously
doesn't. And there are known values of AA.COL_2A where it's all spaces.
The above statement works. My question is "How?"
Thanks!
Rich
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