insert or update columns according weekend - oracle

Question

declare
str varchar2(4000);
i int;
begin
for i in 1 ..31 loop
str:= str || 'col' || i || ' varchar2(2)';
if i < 31 then
str := str || ',';
end if;
end loop;
execute immediate 'create table t1 ('|| str ||')';
end;
/
I'm newbie in pl/sql
this procedure creates t1 table with 31 columns. 31 is day of month (say May). I can't create the procedure which have condition like this :
if col(i) i in ('Sat','Sun') ...
insert into t1 value ('r')
for example, this procedure must insert 'r' into col5,col6,col12,col13 .. columns
because 5th,6th,12th,13th of may in Sun or Sat
BEGIN
FOR i IN 1..31 LOOP
IF( to_char(sysdate-1+i,'DAY') IN ('SAT', 'SUN') )
THEN
INSERT INTO t1 (col(i))
VALUES ('r');
END IF;
END LOOP;
END;
/
I tried with this procedure but there are several errors
where must I correct my mistakes
thanks in advance

Answer 1

I agree with Bob Jarvis that you ought to have a better data model. But just for grins let's assume you have to work with what you've got.
This procedure takes a month and year as parameters, and generates a range of days from them. I have given the MON_T table two columns, MON and YR as a primary key, because I can't help myself.
create or replace procedure gen_month_rec
( p_mon in mon_t.mon%type
, p_yr in mon_t.yr%type )
is
lrec mon_t%rowtype;
empty_rec mon_t%rowtype;
first_dt date;
last_d pls_integer;
begin
lrec := empty_rec;
lrec.mon := p_mon;
lrec.yr := p_yr;
first_dt := to_date('01-'||p_mon||'-'||p_yr, 'dd-mon-yyyy');
last_d := to_number(to_char(last_day(first_dt),'dd'));
for i in 1 .. last_d
loop
if to_char(first_dt-+ (i-1),'DAY') in ('SAT', 'SUN')
then
execute immediate 'begin lrec.col'
||trim(to_char(i))
||' := ''r''; end;';
end if;
end loop;
insert into mon_t values lrec;
end;

Answer 2

I suggest that you read up on the rules of data normalization. It appears that this table suffers from a major problem in that it has what are known as "repeating groups" - in this case, 31 fields for information about each day. You probably need a table with the full date you're interested in, and then the fields which describe that date. Perhaps something like the following:
CREATE TABLE CALENDAR_DAY
(CAL_DATE DATE PRIMARY KEY,
COL NUMBER,
<definitions of other fields needed for each day>);
Given the above your code becomes
DECLARE
dtMonth_of_interest DATE := TRUNC(SYSDATE, 'MONTH');
BEGIN
FOR i IN 0..30 LOOP
IF( to_char(dtMonth_of_interest+i,'DAY') IN ('SAT', 'SUN') )
THEN
INSERT INTO CALENDAR_DAY (CAL_DATE, COL)
VALUES (dtMonth_of_interest + i, 'r');
END IF;
END LOOP;
END;
Hopefully this gives you some ideas.
Share and enjoy.