Try this.
sSQL:='SELECT T.RDB$FIELD_NAME,'+
  'CASE f.RDB$FIELD_TYPE '+
  'WHEN 261 THEN "BLOB" '+
  'WHEN 14 THEN "CHAR ("||F.RDB$FIELD_LENGTH||")"'+
  'WHEN 40 THEN "CSTRING" '+
  'WHEN 11 THEN "D_FLOAT" '+
  'WHEN 27 THEN "NUMERIC (18,"||F.RDB$FIELD_SCALE||")"'+
  'WHEN 10 THEN "FLOAT" '+
  'WHEN 16 THEN "INT64" '+
  'WHEN 8 THEN "INTEGER" '+
  'WHEN 9 THEN "QUAD" '+
  'WHEN 7 THEN "SMALLINT" '+
  'WHEN 12 THEN "DATE" '+
  'WHEN 13 THEN "TIME" '+
  'WHEN 35 THEN "TIMESTAMP" '+
  'WHEN 37 THEN "VARCHAR" '+
  'ELSE "UNKNOWN" '+
  'END,'+
  //'F.RDB$FIELD_LENGTH,'+
  //'F.RDB$FIELD_SCALE,'+
  'T.RDB$FIELD_SOURCE,'+
  'T.RDB$NULL_FLAG,'+
  'T.RDB$DEFAULT_SOURCE '+
  'from RDB$RELATION_FIELDS T '+
  'LEFT JOIN RDB$FIELDS F ON T.RDB$FIELD_SOURCE = F.RDB$FIELD_NAME '+
  'WHERE RDB$RELATION_NAME="'+sTblName+'" '+
  'ORDER BY RDB$FIELD_POSITION'
 
sTblName is the table name.
 

--- On Tue, 3/3/09, Robert martin <rob@...> wrote:

From: Robert martin <rob@...>
Subject: Re: [firebird-support] Fastest way to query tables and views and return no records.
To: firebird-support@yahoogroups.com
Date: Tuesday, March 3, 2009, 12:12 AM






Hi

If you are after field definitions the best way would to just query the
RDB$ tables. RDB$Fields probably has a lot of the data you are looking for.

Thanks
Rob

esbreidenbach wrote:
> Hi,
>
> I have a routine I use in my application which runs a separate query
> on every table and view in the database. The purpose of these queries
> is really just to obtain the field definitions of the underlying
> table, not to return any actual data.
>
> The routine uses the following generic SQL:
>
> Select * from TableName/ViewName where 1 = 0;
>
> My problem is that these queries can run very slowly on views which
> are really meant to have additional where clause statements, and even
> on tables with large numbers of records. The intention of the where
> clause "where 1 = 0" was to eliminate any query activity, but it is
> not working out this way.
>
> Is there a query which I can execute that will run very fast (and
> return no data), or any other ideas on how to do what I want?
>
> Thanks,
>
>
>
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