Insert - Mailing list pgsql-general

I have two tables - p_id.association and p_id.devices

If a new row in p_id.association has a value - say 2 in column mon_function
and a value 5 in column monitoring_fluid I want the new value for
mon_function inserted into table p_id.devices ONLY when 2 AND 5 do not
appear in the same row in p_id.devices.

The following gives me a return of "more than one row" and I can't figure
out what's wrong.

Any thoughts would be appreciated.

Bob

Declare
 xmon_function varchar;

 Begin
 Select mon_function into xmon_function
 From p_id.association
 Where mon_function = new.mon_function;

 If xmon_function = p_id.devices.device_number
 From p_id.association, p_id.devices
 Where p_id.association.monitoring_fluid = p_id.devices.fluid_id
 or p_id.association.monitoring_fluid = p_id.devices.pipe_id
 Then

 Return Null;


 Elseif xmon_function = p_id.devices.device_number
 or xmon_function != p_id.devices.device_number
 From p_id.association, p_id.devices
 Where p_id.association.monitoring_fluid != p_id.devices.fluid_id
 or p_id.association.monitoring_fluid != p_id.devices.pipe_id

 Then
 Insert into p_id.devices (device_number) Values (New.mon_function) ;

 Return Null;
 END if;
 End;