How to compare values with lookup table - sql

Question

I am having one table "Mark" which contains marks of different subjects. If marks fit into one particular range then I should pick up respective rank and insert into marks table itself in column 'rank_sub_1'. could you please help me how can I look up in the table and insert in the column. Below is my table structure.
**Marks**
Subject1_Marks Subject2_Marks
------------------------------
71 22
10 40
**LookupTable**
Rank range1 range2
----------------------
9 10 20
8 21 30
7 31 40
6 41 50
5 51 60
4 61 70
3 71 80
2 81 90
1 91 100
Now I want to check marks of each subject with lookup table which contains the ranges and ranks for different marks obtained.
**Marks**
Subject1_Marks Subject2_Marks Rank_Sub_1 Rank_Sub_2
------------------------------------------------------
71 22
10 40
If marks fit into one particular range then I should pick up respective rank and insert into marks table itself in column 'rank_sub_1'. could you please help me how can I look up in the table and insert in the column.

Answer 1

(Considering there is no overlapping in range values)
Take two instances of lookuptable and join first with subject1_marks and second with subject2_marks. Here i haven't used LEFT JOINS as i am assuming your subject marks will fall under 1 range for sure. If you are not sure about that, please use left joins and handle null values as per your requirement for columns RANK_SUB_1 and RANK_SUB_2
WITH LOOKUPTABLE_TMP AS (SELECT * FROM LOOKUPTABLE)
SELECT M.*, L1.RANK AS RANK_SUB_1, L2.RANK AS RANK_SUB_2
FROM MARKS M , LOOKUPTABLE_TMP L1, LOOKUPTABLE_TMP L2
WHERE M.SUBJECT1_MARKS BETWEEN L1.RANGE1 AND L1.RANGE2
AND M.SUBJECT2_MARKS BETWEEN L2.RANGE1 AND L2.RANGE2
Then MERGE the data into table MARKS.
Solution:
MERGE INTO MARKS MS
USING
(
SELECT M.SUBJECT1_MARKS, M.SUBJECT2_MARKS, L1.RNK AS RANK_SUB_1, L2.RNK AS RANK_SUB_2
FROM MARKS M , LOOKUPTABLE L1, LOOKUPTABLE L2
WHERE M.SUBJECT1_MARKS BETWEEN L1.RANGE1 AND L1.RANGE2
AND M.SUBJECT2_MARKS BETWEEN L2.RANGE1 AND L2.RANGE2
GROUP BY M.SUBJECT1_MARKS, M.SUBJECT2_MARKS, L1.RNK, L2.RNK
) SUB
ON (MS.SUBJECT1_MARKS=SUB.SUBJECT1_MARKS AND MS.SUBJECT2_MARKS =SUB.SUBJECT2_MARKS)
WHEN MATCHED THEN UPDATE
SET MS.RANK_SUB_1=SUB.RANK_SUB_1, MS.RANK_SUB_2=SUB.RANK_SUB_2;
Tested on below schema and data as per your question's details.
CREATE TABLE MARKS (SUBJECT1_MARKS NUMBER, SUBJECT2_MARKS NUMBER , RANK_SUB_1 NUMBER, RANK_SUB_2 NUMBER)
INSERT INTO MARKS (SUBJECT1_MARKS , SUBJECT2_MARKS ) VALUES (71, 22);
INSERT INTO MARKS (SUBJECT1_MARKS , SUBJECT2_MARKS ) VALUES (10, 40);
CREATE TABLE LOOKUPTABLE (RNK NUMBER, RANGE1 NUMBER , RANGE2 NUMBER)
INSERT INTO LOOKUPTABLE VALUES (9, 10, 20);
INSERT INTO LOOKUPTABLE VALUES (8, 21, 30);
INSERT INTO LOOKUPTABLE VALUES (7, 31, 40);
INSERT INTO LOOKUPTABLE VALUES (6, 41, 50);
INSERT INTO LOOKUPTABLE VALUES (5, 51, 60);
INSERT INTO LOOKUPTABLE VALUES (4, 61, 70);
INSERT INTO LOOKUPTABLE VALUES (3, 71, 80);
INSERT INTO LOOKUPTABLE VALUES (2, 81, 90);
INSERT INTO LOOKUPTABLE VALUES (1, 91, 100);
Thanks!!

Answer 2

I think thisupdatestatement should do what you want:
UPDATE Marks m
SET Rank_Sub_1 = (SELECT l.Rank
FROM LookupTable l
WHERE m.Subject1_Marks BETWEEN l.range1 AND l.range2)
WHERE EXISTS (
SELECT 1
FROM LookupTable l
WHERE m.Subject1_Marks BETWEEN l.range1 AND l.range2
);
Sample SQL Fiddle
If you want to update the value forRank_Sub_2at the same time you can do this:
UPDATE Marks m
SET Rank_Sub_1 = (SELECT l.Rank
FROM LookupTable l
WHERE m.Subject1_Marks BETWEEN l.range1 AND l.range2)
,Rank_Sub_2 = (SELECT l.Rank
FROM LookupTable l
WHERE m.Subject2_Marks BETWEEN l.range1 AND l.range2)
Sample SQL Fiddle

Answer 3

Consider the design below which eliminates the possibility of overlaps or gaps. Although I usually use this technique with dates, any data that defines an unbroken sequence will work the same way. The idea is that you only define where the range starts. It is understood that the range stops at the last value possible less than the next higher range. However, notice I added a tenth rank, in case values less than 10 are possible. Any values greater than 100 will, of course, show as rank 1.
with
Lookup( Rank, Cutoff )as(
select 1, 91 union all
select 2, 81 union all
select 3, 71 union all
select 4, 61 union all
select 5, 51 union all
select 6, 41 union all
select 7, 31 union all
select 8, 21 union all
select 9, 10 union all
select 10, 0
),
Marks( Mark1, Mark2 )as(
select 71, 22 union all
select 10, 40 union all
select 21, 101
)
select Mark1, l1.Rank as Rank1, Mark2, l2.Rank as Rank2
from Marks m
join Lookup l1
on l1.Cutoff =(
select Max( Cutoff )
from Lookup
where Cutoff <= m.Mark1 )
join Lookup l2
on l2.Cutoff =(
select Max( Cutoff )
from Lookup
where Cutoff <= m.Mark2 );
The output:
Mark1 Rank1 Mark2 Rank2
----------- ----------- ----------- -----------
71 3 22 8
10 9 40 7
21 8 101 1