Problem with select and null - Mailing list pgsql-general

From Frank Millman
Subject Problem with select and null
Date
Msg-id 000801c48e7a$362bc910$0401a8c0@chagford.com
Whole thread Raw
Responses Re: Problem with select and null  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
Hi all
 
'SELECT (null * null)' returns null
 
'SELECT (null - 0)' returns null
 
'SELECT ((null * null) - 0)' gives the following error -
ERROR: operator does not exist: "char" - integer
 
Why does this statement give an error? I would expect it to return null.
 
Under some circumstances my program generates the above select statement, so this is not an academic question.
 
Platform is PostgreSQL 7.4.1, running on Redhat 9.
 
Is this a bug? Is there any workaround? My workaround for now is to 'coalesce' to zero all the values which could return null. The result is zero instead of null, which is not what I want, but I can live with it in the short term.
 
TIA for any suggestions.
 
Frank Millman

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