subqueries and qualification of table names

[Kevin Murphy <murphy@xxxxxxxxxxxxxxx>]

I have a query which didn't work properly until I fully qualified 
columns used in a a subquery with the appropriate table names.  The 
reason is that both tables have a column named 'chromosome' used in the 
subquery.  In the following query, PG treats the phrase "and chromosome 
= chromosome" as "and genetic.chromosome = genetic.chromosome".  I.e. 
it treats:

---
# select chromosome, layer, rank,
        (select refsnp_id
                from genetic
                where extended_frame = True
                        and chromosome = chromosome
                        and gl_left = rank)
from framework
where name = 'D3S3610'
        and layer = 'GL';
---

as:
---
select chromosome, layer, rank,
        (select refsnp_id
                from genetic
                where genetic.extended_frame = True
                        and genetic.chromosome = genetic.chromosome
                        and genetic.gl_left = framework.rank)
from framework
where name = 'D3S3610'
        and layer = 'GL';
---

Is that the appropriate SQL behavior?  Personally I don't care; I'm 
just curious.

Thanks,
Kevin Murphy


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