Hello All,
Attempting to select two different column types with COALESCE returns
this error:
ERROR: COALESCE types smallint and character varying cannot be matched
Attempting the same thing with a CASE statement returns a similar error:
ERROR: CASE types smallint and character varying cannot be matched
I also checked Oracle's NVL command, and it throws a similar error.
Clearly, I'm not supposed to intermix two different column types into a
SELECT statement. This is because the engine needs to return a set
given the criteria, and it's difficult to do that with criteria that
/depends on the data/, yes?
Could someone explain a/the more formal reason why I can't do what I'm
trying to do?
The relevant part of my SELECT statement:
SELECT
...,
COALESCE(f.number, f.name),
...
FROM
...,
field AS f,
...
WHERE
...
;
f.number ∈ SMALLINT
f.name ∈ CHARACTER VARYING
Thank you in advance!
Kevin
P.S. If something gets lost in bit/encoding translation, ∈ = "Element Of"
