Selecting max date for specific 'operation' code

Question

I have the following scenario: a history table that keeps track of the 'operation' and the date of the operation. For example, the operation field can have a code of U (for update), C (for closed), O (for re-opened), A (for approved), etc.
The goal of this history table is to keep track of all of the modifications made. Hence, a particular record of interest can have more than one 'U' operation documented, C operation, etc.
How can I choose the max date for each operation.
I was diong the following in my PL/SQL:
BEGIN
SELECT operation_code, o_date, user INTO lv_operation_code, lv_date, lv_user FROM table1 WHERE unique_id = pv_id AND operation_code = U' AND o_date = (SELECT max(o_date) FROM table1 WHERE unique_code = pv_id);
EXCEPTION
WHEN NO_DATA_FOUND THEN NULL;
END;
I then have another begin statement for the 'C' operation, etc.

Answer 1

Hi,
OraclePolzovatel wrote:
... I was diong the following in my PL/SQL:
BEGIN
SELECT operation_code, o_date, user INTO lv_operation_code, lv_date, lv_user FROM table1 WHERE unique_id = pv_id AND operation_code = U' AND o_date = (SELECT max(o_date) FROM table1 WHERE unique_code = pv_id);
EXCEPTION
WHEN NO_DATA_FOUND THEN NULL;
END;
I then have another begin statement for the 'C' operation, etc.Are you sure that's what you're doing? There seem to be errors, such as unmatched quotes.
Instead of doing a single SELECT with something like "operation_code = 'U'" in the WHERE-clause, you could write a cursor with "GROUP BY operation_code".