SELECT query based on mentioned result table - Oracle SQL - sql

Question

I have 3 tables.
TABLE1 with one column ROLL_NO
CREATE TABLE TABLE1 (ROLL_NO NUMBER(3) NOT NULL);
TABLE2 with 3 columns ROLL_NO, CLASS, SEC
CREATE TABLE TABLE2 (ROLL_NO NUMBER(3) NOT NULL, CLASS NUMBER(3) NOT NULL, SEC NUMBER(3) NOT NULL);
TABLE3 with 3 columns ROLL_NO, CODE, AMT
CREATE TABLE TABLE3 (ROLL_NO NUMBER(3) NOT NULL, CODE VARCHAR2(3) NOT NULL, AMT NUMBER(3) NOT NULL);
INSERT INTO TABLE1 VALUES (101);
INSERT INTO TABLE1 VALUES (102);
INSERT INTO TABLE1 VALUES (103);
INSERT INTO TABLE1 VALUES (104);
----------------------------------
INSERT INTO TABLE2 VALUES (101,1, 12);
INSERT INTO TABLE2 VALUES (102,1, 12);
INSERT INTO TABLE2 VALUES (103,1, 12);
INSERT INTO TABLE2 VALUES (104,1, 12);
--------------------------------------
INSERT INTO TABLE3 VALUES (101, 'A2', 100);
INSERT INTO TABLE3 VALUES (101, '10', 100);
INSERT INTO TABLE3 VALUES (102, 'B3', 200);
INSERT INTO TABLE3 VALUES (102, '10', 200);
INSERT INTO TABLE3 VALUES (103, '04', 300);
The SQL query which mentioned below:
SELECT T1.ROLL_NO,
T2.CLASS,
T2.SEC,
NVL(T3.CODE,0) AS CODE,
NVL(T3.AMT, 0) AS AMT
FROM TABLE1 T1
JOIN TABLE2 T2 ON T1.ROLL_NO = T2.ROLL_NO
LEFT JOIN TABLE3 T3 ON T1.ROLL_NO = T3.ROLL_NO
WHERE T1.ROLL_NO IN (101,102,103,104);
If we don't find any record i.e. CODE and AMT for particular ROLL_NO, by default we are assigning as 0.
The result for above query:
ROLL_NO CLASS SEC CODE AMT
-------------------------------------
101 1 12 A2 100
101 1 12 10 100
102 1 12 B3 200
102 1 12 10 200
103 1 12 4 300
104 1 12 0 0
I am looking for a query in such a way that
a) if particular ROLL_NO has CODE 10 and also additional CODE values other than 10 then get that row which has CODE as 10 in the result table.
b) if particular ROLL_NO don't have CODE 10 but has other additional CODE values then get that row in the result table.
In previous table, ROLL_NO 101 and 102 comes under case 'a' and 103, 104 comes under case 'b'
Final result should be
ROLL_NO CLASS SEC CODE AMT
-------------------------------------
101 1 12 10 100
102 1 12 10 200
103 1 12 4 300
104 1 12 0 0
I am looking for a query to get the above result but I am not able to get it. Till now, I tried using RANK function by partitioning on ROLL_NO and order by CODE in descending and select 1st row in each partition but it doesn't work if particular ROLL_NO have additional code greater than 10.

Answer 1

You can use analytic function ROW_NUMBER() and it should work:
select roll_no, class, sec, code, amt
from (SELECT T1.ROLL_NO,
T2.CLASS,
T2.SEC,
NVL(T3.CODE,0) AS CODE,
NVL(T3.AMT, 0) AS AMT,
--analytic function
row_number() over (partition by t1.roll_no order by NVL(T3.CODE,0) desc) as row_num
FROM TABLE1 T1
JOIN TABLE2 T2 ON T1.ROLL_NO = T2.ROLL_NO
LEFT JOIN TABLE3 T3 ON T1.ROLL_NO = T3.ROLL_NO
WHERE T1.ROLL_NO IN (101,102,103,104)) t
where t.row_num = 1;

Answer 2

You simply need a ROW_NUMBER() function to achieve your desired result -
SELECT T1.ROLL_NO,
T2.CLASS,
T2.SEC,
NVL(T3.CODE,0) AS CODE,
NVL(T3.AMT, 0) AS AMT
FROM TABLE1 T1
JOIN TABLE2 T2 ON T1.ROLL_NO = T2.ROLL_NO
LEFT JOIN (SELECT ROLL_NO, CODE, AMT,
ROW_NUMBER() OVER(PARTITION BY ROLL_NO ORDER BY CODE DESC) RN
-- If you have code greater than 10 also you have to use a CASE statement instead of simple order by clause
FROM TABLE3) T3 ON T1.ROLL_NO = T3.ROLL_NO
AND RN = 1
WHERE T1.ROLL_NO IN (101,102,103,104);