How to get max date in variable using dynamic query

Question

Hi,
the following code gets all dates from sourcetable i want only max date , so i thought max function can be added and it will work
but still i have to create a table for one value(scalar) can get it in any other effeciant way.
declare
TYPE date_string IS TABLE OF VARCHAR(1000);
date_obj date_string;
BEGIN
EXECUTE IMMEDIATE 'SELECT to_char('''||day1||'-'||month1||'-'||year1||''') FROM '||source_schema||'.'|| sourcetable ||'' bulk collect INTO date_obj;
FOR indx IN date_obj.FIRST..date_obj.LAST loop
dbms_output.put_line(
date_obj(indx));
END loop;
DBMS_OUTPUT.PUT_LINE('Sample output');
END;
yours sincerely

Answer 1

944768 wrote:
the following code gets all dates from sourcetableNo it doesn't. What is the datatype of day1, month1 and year1? They cannot be DATE datatypes otherwise your TO_CHAR would fail with all that concatenation going on. And your TO_CHAR is returning a VARCHAR2 datatype... so you cannot say that it is getting all dates... because there are no DATE datatypes returned. It's getting a lot of strings, but certainly not DATE's.
i want only max date , so i thought max function can be added and it will work You can use the MAX function on a DATE datatype, but not on strings (at least not in the way you intend it to work).
Converting it to a DATE before doing the MAX will allow you to get the maximum date (assuming the date format is correct)
EXECUTE IMMEDIATE 'SELECT max(to_date(to_char('''||day1||'-'||month1||'-'||year1||'''),''DD-MM-YYYY'')) FROM  '||source_schema||'.'|| sourcetable ||'' bulk collect INTO date_obj;Then you will find have the other issues...
a) you are then going to be fetching your DATEs in to a collection of VARCHAR strings. (Not even VARCHAR2, very poor). This should be DATE datatype
b) you are bulk collecting into a collection, when you are using MAX which will return a single value in your example
And you really should address the design issues:
c) why are day, month and year, not being stored in the database as a single DATE datatype in the first place
d) why does your code not know the name of the table it's querying requiring the use of very poor dynamic SQL techniques.
e) why are you loading data in a collection in expensive PGA memory... what can't you do in SQL that requires you to collect the data into memory first?