Need help with special select case

Question

Oracle DB 12c, I think 12.1.2
drop table person_tests;
create table person_tests (
person_id number,
test_type_id varchar2(1),
test_date date
insert into person_tests (person_id,test_type_id,test_date) values (1,'A',to_date('01012000','MMDDYYYY'));
insert into person_tests (person_id,test_type_id,test_date) values (1,'A',to_date('01022000','MMDDYYYY'));
insert into person_tests (person_id,test_type_id,test_date) values (1,'B',to_date('01032000','MMDDYYYY'));
insert into person_tests (person_id,test_type_id,test_date) values (1,'B',to_date('01042000','MMDDYYYY'));
insert into person_tests (person_id,test_type_id,test_date) values (1,'C',to_date('01052000','MMDDYYYY'));
insert into person_tests (person_id,test_type_id,test_date) values (2,'C',to_date('01062000','MMDDYYYY'));
insert into person_tests (person_id,test_type_id,test_date) values (3,'A',to_date('01072001','MMDDYYYY'));
insert into person_tests (person_id,test_type_id,test_date) values (3,'A',to_date('01082000','MMDDYYYY'));
insert into person_tests (person_id,test_type_id,test_date) values (3,'B',to_date('01092000','MMDDYYYY'));
insert into person_tests (person_id,test_type_id,test_date) values (3,'B',to_date('01102000','MMDDYYYY'));
insert into person_tests (person_id,test_type_id,test_date) values (3,'C',to_date('01102000','MMDDYYYY'));
Persons as participating in certain tests: A, B and C where each test is tagged with a date when done.
I need to output only people that completed 2 tests of type A, 2 tests of type B and 1 test of type C. I have to display the test type and the date of the most recent of those tests. In the example above, desired output would be
1 C            05-JAN-00
3 A            07-JAN-01
Hope this problem definition makes sense

Answer 1

Hi,
Sorry, I missed the requirement about showing the most recent test_type_id.
Assuming the date to be shown is the date the minimum requirements were fulfilled (whether of not gratutitous tests came afterwrds), you can do something like this:
WITH    got_r_num    AS
    SELECT  person_id, test_type_id, test_date
    ,       ROW_NUMBER () OVER ( PARTITION BY  person_id, test_type_id
                                 ORDER BY      test_date
                               )   AS r_num
    FROM    person_tests
    WHERE   test_type_id  IN ('A', 'B', 'C')
SELECT    person_id
,         MIN (test_type_id) KEEP (DENSE_RANK LAST ORDER BY  test_date)  AS last_test_type
,         MAX (test_date)                                                AS last_test_date
FROM      got_r_num
WHERE     r_num  <= CASE  test_type_id
                        WHEN  'A'  THEN  2
                        WHEN  'B'  THEN  2
                        WHEN  'C'  THEN  1
                    END
GROUP BY  person_id
HAVING    COUNT (*)  = 5  -- 2 'A's  +  2 'B's  +  1 'C'
What test_type_id would you want to display in case of a tie for the latest test?
I just saw your post saying that a person with 3 or more type 'A' tests should be excluded.  In that case, my original solution (with = in the main WHERE clause) is what you want; only used LAST to get the latest test_type_id.  The solution in this message is for the situation where you don't care if someone had 3 or more 'A's, but you want to ignore all but the first 2.