Re: JDBC

If I try to return a ResultSet the class will not compile with the
message that boolean cannot be converted to a ResultSet. And this is
in synch with the documentation that states the "exists" subquery will
return a boolean -- not a ResultSet.

There are a number of sites that indicate the statement is the way to
find out if a table exists. Are the sites for an older version of PG?
I'm running on 10.

Thanks.

On Sun, Jun 10, 2018 at 1:44 PM, David G. Johnston
<david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
> On Sunday, June 10, 2018, Chuck Davis <cjgunzel(at)gmail(dot)com> wrote:
>>
>>
>> try {
>> result = stat.execute("select exists (select 1 from
>> information_schema.tables where table_name = 'entities')");
>> System.out.println("the checkEntity returned a result of "
>> + result);
>> } catch (SQLException ex) {
>>
>> Logger.getLogger(ClientConstants.class.getName()).log(Level.SEVERE,
>> null, ex);
>> result = false;
>> return result;
>> }
>
>
> Your query is putting "false" into cell (0,0) of a ResultSet. You are
> failing to even look at the resultset to see if it holds a true or false.
>
> The query should never fail since you aren't using the table name directly
> but are checking for it as a value in another table that always exists. The
> inner query returns zero records when the table doesn't exist and the EXISTS
> construct converts that to false.
>
> David J.
>