Q:

handle relation not found in postgresql

I trying to write a query in which for now the relation does not exists, there are many tables invovled in the sub query and 1 of them does not exists as of now.
Is there a way i can write the query so that it returns 0 in case the relation does not exists
for example my query is "Select emp_name from employee AS name limit 1"
is there a way to rewrite it to return 0 or null is the relation does not exists?
Any help would be appreciated. Thanks.

A:

The only way to do this is with dynamic SQL, either in the client or in plpgsql. 
You can build your query using queries against information_schema to see which tables exist, then pass it to PL/PgSQL's EXECUTE to actually run the assembled query.
The format function's %I format specifier will be useful to you, as will the USING option to EXECUTE.

