Convert a value based on range - sql

Question

I need to convert a number to another value based on a range:
ie:
7 = "A"
106 = "I"
I have a range like this:
from to return-val
1 17 A
17 35 B
35 38 C
38 56 D
56 72 E
72 88 F
88 98 G
98 104 H
104 115 I
115 120 J
120 123 K
123 129 L
129 infinity M
The values are fixed and do not change.
I was thinking a lookup table would be required, but is there a way it could be done with a function on an analytics function inside of oracle?

Answer 1

Think I would use a mapping table:
mapping:
to ret
17 A
38 B
Select Max(ret)
From mapping
Where x <= to
You could also use CASE WHEN:
Select Case When x <= 17 Then 'A'
When x <= 35 Then 'B'
When x <= 38 Then 'C'
...
Else 'M' End
From your_table

Answer 2

SQL servers are designed such that operating on a table is faster than anything else -- particularly when that table will only have 13 rows.

Answer 3

I would create a function, in oracle, since it should be more efficient than doing a table lookup (no roundtrip to disk will ever be involved).
CREATE OR REPLACE Function ValueFromRange
( n IN number )
RETURN varchar2
IS
ret varchar2;
BEGIN
ret := -1; -- UNDEFINED?
IF n >= 1 and n <= 17 THEN
ret := 'A';
ELSIF n >= 18 and n <= 35 THEN
ret := 'B';
ELSIF n >= 36 and n <= 38 THEN
ret := 'C';
ELSIF n >= 39 and n <= 56 THEN
ret := 'D';
ELSIF n >= 57 and n <= 72 THEN
ret := 'E';
ELSIF n >= 73 and n <= 88 THEN
ret := 'F';
ELSIF n >= 89 and n <= 98 THEN
ret := 'G';
ELSIF n >= 99 and n <= 104 THEN
ret := 'H';
ELSIF n >= 105 and n <= 115 THEN
ret := 'I';
ELSIF n >= 116 and n <= 120 THEN
ret := 'J';
ELSIF n >= 121 and n <= 123 THEN
ret := 'K';
ELSIF n >= 124 and n <= 129 THEN
ret := 'L';
ELSIF n >= 130 THEN
ret := 'M';
END IF;
RETURN ret;
END;