I think this is a consequence of the internal representations of text
and varchar and char being identical, so that the cast finctions think
there's nothing to do.
I think this is fixed in 6.5. A work around for 6.4 is to apply
afunction that does nothing to the text: I've used btrim() in the past
(since I usually want to get rid of trailing whitespace anyway:
test=> select btrim(chromosome) || btrim(arm) as locus from experiment;
Stuart Rison wrote:
> Dear All,
> I'm trying to get the concatenation operator (||) to work with different
> character variables (i.e. varchar and bpchar)... and failing.
> consider the following:
> create table experiment (
> chromosome varchar(2), // that for chromosomes 1-22 and X and Y
> arm char(1) // can only be one of 'q' or 'p'
> insert into experiment values ('22','q');
> insert into experiment values ('17','p');
> select * from experiment;
> (2 rows)
> I want to select a field as the concatenation of the chromosome and the arm...
> cgh=> select chromosome || arm as locus from experiment;
> ERROR: There is more than one possible operator '||' for types 'varchar'
> and 'b
> You will have to retype this query using an explicit cast
Ross J. Reedstrom, Ph.D., <reedstrm(at)rice(dot)edu>
NSBRI Research Scientist/Programmer
Computer and Information Technology Institute
Rice University, 6100 S. Main St., Houston, TX 77005
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