Can't write sql query with RANK() function - sql

Question

In my application I need to retrieve the best file from database with the following rules:
file, that has the most number of upvotes - priority 1
file, that has the most number of comments - priority 2
If there are only files that have no upvotes and no comments, then pick up just the random one.
My tables:
CREATE TABLE "FILES"
( "ID" NUMBER,
"OBJ_ID" NUMBER,
"NAME" VARCHAR2(30 BYTE)
) ;
CREATE TABLE "UPVOTES"
( "ID" NUMBER,
"TO_ID" NUMBER,
"TO_TYPE" NUMBER
) ;
COMMENT ON COLUMN "UPVOTES"."TO_TYPE" IS '0 obj, 1 file, 2 comment';
CREATE TABLE "COMMENTS"
( "ID" NUMBER,
"OBJ_ID" NUMBER,
"CONTENT" VARCHAR2(20 BYTE),
"TO_TYPE" NUMBER,
"TO_ID" NUMBER
) ;
COMMENT ON COLUMN "COMMENTS"."TO_TYPE" IS '0 object, 1 file';
Insert into FILES (ID,OBJ_ID,NAME) values ('1','1','best file for obj id = 1');
Insert into FILES (ID,OBJ_ID,NAME) values ('2','1','file obj1');
Insert into FILES (ID,OBJ_ID,NAME) values ('3','1','file obj1');
Insert into FILES (ID,OBJ_ID,NAME) values ('4','2','best file for obj id = 2');
Insert into FILES (ID,OBJ_ID,NAME) values ('5','2','file obj2');
Insert into FILES (ID,OBJ_ID,NAME) values ('6','3','only one file obj 3');
Insert into FILES (ID,OBJ_ID,NAME) values ('7','4','probilem file obj 4');
Insert into UPVOTES (ID,TO_ID,TO_TYPE) values ('1','1','1');
Insert into UPVOTES (ID,TO_ID,TO_TYPE) values ('2','1','1');
Insert into UPVOTES (ID,TO_ID,TO_TYPE) values ('3','7','0');
Insert into UPVOTES (ID,TO_ID,TO_TYPE) values ('4','2','0');
Insert into UPVOTES (ID,TO_ID,TO_TYPE) values ('5','2','0');
Insert into UPVOTES (ID,TO_ID,TO_TYPE) values ('6','2','0');
Insert into COMMENTS (ID,OBJ_ID,CONTENT,TO_TYPE,TO_ID) values ('1','1','comment 1','1','2');
Insert into COMMENTS (ID,OBJ_ID,CONTENT,TO_TYPE,TO_ID) values ('2','1','comment 2','1','2');
Insert into COMMENTS (ID,OBJ_ID,CONTENT,TO_TYPE,TO_ID) values ('3','2','comment 3','1','4');
My sql query:
SELECT obj_id, name FROM (
SELECT obj_id, name, rank, ROW_NUMBER() OVER (PARTITION BY obj_id ORDER BY rank) rownumb FROM (
SELECT f.obj_id, f.name, RANK() OVER (PARTITION BY f.obj_id ORDER BY COUNT(v.id) DESC, COUNT(DISTINCT com.id) DESC) rank
FROM files f
LEFT OUTER JOIN upvotes v
ON f.id = v.to_id
LEFT OUTER JOIN comments com
ON f.id = com.to_id
WHERE (v.to_type = 1 OR v.to_type IS NULL)
AND (com.to_type = 1 OR com.to_type IS NULL)
GROUP BY f.obj_id, f.name
)
)
WHERE rownumb = 1;
Expected result:
obj_id file name
1 best file for obj id = 1
2 best file for obj id = 2
3 only one file obj 3
4 probilem file obj 4
The problem is with the line:
(v.to_type = 1 OR v.to_type IS NULL)
It fails, because there are upvotes for objects (TO_TYPE = 0) with the same TO_ID as file ID, but I still need to count upvotes for files (TO_TYPE = 1).
Can somebody help me to figure it out?
I use Oracle Database 11g XE R2.

Answer 1

Replace
FROM files f
LEFT OUTER JOIN upvotes v
ON f.id = v.to_id
LEFT OUTER JOIN comments com
ON f.id = com.to_id
WHERE (v.to_type = 1 OR v.to_type IS NULL)
AND (com.to_type = 1 OR com.to_type IS NULL)
by
FROM files f
LEFT OUTER JOIN upvotes v ON f.id = v.to_id AND v.to_type = 1
LEFT OUTER JOIN comments com ON f.id = com.to_id AND com.to_type = 1