create table orders (
id int default nextval('orders_seq') primary key,
order_name varchar( 64 ),
cust_id int not null references users(id),
is_confirmed boolean null,
creation_moment timestamp not null default now(),
confirm_moment timestamp not null default now()
);

create table weeks (
id t_week_id primary key,
first_day date not null,
last_day date not null
);

select extract (week from timestamp (orders.last_day))

create or replace function sp_timestring (in p_date_to_cover varchar ( 50 ))
returns text
as $$
select to_char (timestamp , text)
$$ language sql;

create or replace function sp_timestring (in p_date_to_cover varchar ( 50 ))
returns text
as $$
select to_char ( current_timestamp,'WW');
$$ language sql;

create or replace function sp_timestring (@timetext text)
returns text
as $$
declare @timetext text
select to_char ( current_timestamp,'WW') = @timetext;
select extract (week from timestamp, @timetext);
$$ language sql;

create or replace function sp_timestring (timetext text)
returns  int
as $$ 
select to_char ( current_timestamp,'WW')as timetext;
select extract (week from timestamp [color=yellow]timetext [/color]);
$$ language sql;