parse error when executing a simple plpgsql function

Hi,

When I execute the function get_column as select * from
get_column('dat', 1), I have a parse error like this:
parse error at or near ";"

Here is the code for the get_column() function:

create or replace function get_column(char(3), int8) returns setof daf
as
'
declare
database alias for $1;
begin
if database = ''dat'' then
select * from data_get_column($2);
else if database = ''mat'' then
select * from material_get_column ($2);
else if database = ''act'' then
select * from activity_get_column ($2);
end if;
end;
'
language 'plpgsql';

And here is a prototype of the methods data_get_column():

create or replace function data_get_column(int8) returns setof daf as
'
declare
r daf%rowtype;
begin
for r in select father_id, denom, abbrev from data_columns
return next r;
end loop;
return;
end
'
language 'plpgsql';

And here the type used:
create type daf as (father_id int8, denom varchar(40), abbrev
varchar(15));

Moreoever I want to make them better to return only one result of type
daf as the primary key of data_columns is id. Can you help me to design
this kind of function ?

Thank you very much for your attention,

Louis Foucart.