Using date in ref cusor with pl/sql - date

Question

I have a var: acc_date with type date.
It takes its value from a cursor and when I insert its value to logger table as:
insert into logger values(1,acc_date);
the out put when a select it from logger is
1 01-JAN-10
but when i use it to compare with another Date value in another cursor as
OPEN c_get_date_id
for 'SELECT Date_D.DATEKEY from Date_D where Date_D.DATEVALUE='||acc_date;
EXIT WHEN c_get_date_id%NOTFOUND;
FETCH c_get_date_id
INTO date_id;
insert into logger values (1,'Now with date_id'||date_id);
CLOSE c_get_date_id;
an error occurs:
Error report:
ORA-00904: "JAN": invalid identifier
ORA-06512: at "HW.FILLFACT", line 82
ORA-06512: at line 1
00904. 00000 - "%s: invalid identifier"
*Cause:
*Action:
strong text

Answer 1

You need at least add some quotes around the date:
....' where Date_D.DATEVALUE='''||acc_date||'''';
Double apostrophes within a string will be concatenated to a single apostrophe, so that the expression becomes
where Date_D.DATEVALUE='....';
In order to make the thing more foolprof, I'd also add a specific to_date:
.... ' where Date_D.DATEVALUE=to_date(''' || acc_date || ', ''dd-mon-yy'')';

Answer 2

At the moment your dynamic query is being interpreted as:
SELECT Date_D.DATEKEY from Date_D where Date_D.DATEVALUE=01-JAN-10
The error is because string representation of the date isn't being quoted, so it's seeing JAN as an identifier - and nothing matches that name. You could enclose the date value in quotes:
open c_get_date_id
for 'SELECT Date_D.DATEKEY from Date_D where Date_D.DATEVALUE='''||acc_date||'''';
But you're treating the date as a string, and forcing conversion of all your table values to strings to be compared, using your session's NLS_DATE_FORMAT. It would be better to compare it as a date (although this somewhat assumes all your values have the time portion set to midnight):
open c_get_date_id
for select date_d.datekey from date_d where date_d.datevalue = acc_date;
Your exit is in the wrong place though, and you aren't looping, so maybe you want:
open c_get_date_id
for select date_d.datekey from date_d where date_d.datevalue = acc_date;
loop
fetch c_get_date_id into date_id;
exit when c_get_date_id%notfound;
insert into logger values (1, 'Now with date_id'||date_id);
end loop;
close c_get_date_id;
If you only have one value in the first place though, you probably don't want a loop or cursor at all, and could do a simple select ... into instead:
select date_d.datekey into date_id from date_d
where date_d.datevalue = acc_date;
insert into logger values (1, 'Now with date_id'||date_id);
Though of course that would error if you had no matching date in your table, or more than one, and you'd need to deal with that - but then I guess you'd want to anyway.