Join two tables on multiple conditions Using Oracle SQL - sql

Question

I have a 2 Tables with below structures
Table 1-- Containing Values like this.
OTHER_CODE
CAPACITY_CODE
Result
A
1
A
5
A
9
A
(null)
B
2
B
6
B
2
Table_2- With Values Like
OTHER_CODE
CAPACITY_CODE
Result
A
1
A
A
5
B
A
(null)
C
A
ELSE
D
B
ALL
E
(null)
ALL
F
I need to Join Table_1 with Table_2 on basis of columns OTHERCODE and CAPACITYCODE and update values in Column Result of Table**1 **using a Merge statement.
I need to handle and match Values based on ELSE and ALL values too.
Check for Direct Match
Check if ALL or ELSE condition
The Final TABLE_1 must look like
OTHER_CODE
CAPACITY_CODE
Result
Explanation
A
1
A
Direct Join
A
5
B
Direct Join
A
9
D
Satsifying ELSE condition
A
(null)
C
Direct join with NVL handling
B
2
E
As Value for CapacityCode in TableB is ALL
B
6
E
As Value for CapacityCode in TableB is ALL
B
2
E
As Value for CapacityCode in TableB is ALL
I Tried Joining both the tables but the was unable to satisfy Else and ALL conditions. Hope if someone can help me on this.
There are Several **Result ** Columns like , Result 1 ,2 in both tables which needs to be updated using the same logic.
Thanks in Advance.

Answer 1

here is a fiddle to work on https://dbfiddle.uk/FMKdWzQT
I got the query working. by using a case statement and assigning a number so I could use max then I just remove the number.
SELECT a.other_code,
a.capacity_code,
(
SELECT SUBSTR(max(
CASE WHEN b.other_code = a.other_code AND a.capacity_code = b.capacity_code THEN concat('3',b.myresult)
WHEN b.other_code = a.other_code AND a.capacity_code is null and b.capacity_code is null THEN concat('2',b.myresult)
WHEN b.other_code = a.other_code AND b.capacity_code in ('ELSE', 'ALL') THEN concat('1',b.myresult)
else null end),2)
FROM table2 b ) as myresult
FROM table1 a
however I can not get the update to work. I tried a merge it is give me the unstable row error and I tried an update select but that is giving me single row subquery error so maybe someone else can take a look at the fiddle. here was my attempt at the update.
UPDATE table1
SET myresult = (
SELECT myresult
FROM (
SELECT a.other_code,
a.capacity_code,
(
SELECT SUBSTR(max(
CASE WHEN b.other_code = a.other_code AND a.capacity_code = b.capacity_code THEN concat('3',b.myresult)
WHEN b.other_code = a.other_code AND a.capacity_code is null and b.capacity_code is null THEN concat('2',b.myresult)
WHEN b.other_code = a.other_code AND b.capacity_code in ('ELSE', 'ALL') THEN concat('1',b.myresult)
else null end),2)
FROM table2 b ) as myresult
FROM table1 a
)t2
WHERE table1.other_code = t2.other_code and nvl(table1.capacity_code,'x') = nvl(t2.capacity_code,'x')
);