SQL: How do dynamically parse ranges from min to next min? - sql

Question

I am trying to figure out how (or see if possible) I can grab the minimum value of 'TEST' and get just the next minimum value of 'TEST', then join again and go after the 2nd minimum value, etc, etc.
Table1
ID TEST
A12 1
A12 2
A12 3
A12 5
A12 8
B35 1
B35 3
Results I'm after:
ID RANGE1 RANGE2
A12 1 2
A12 2 3
A12 3 5
A12 5 8
B35 1 3
table code I'm using:
WITH FRED AS
(
SELECT 'A12' AS ID
, 1 AS TEST
UNION
SELECT 'A12' AS ID
, 2 AS TEST
UNION
SELECT 'A12' AS ID
, 3 AS TEST
UNION
SELECT 'B35' AS ID
, 1 AS TEST
UNION
SELECT 'B35' AS ID
, 2 AS TEST
)
SELECT *
FROM FRED F

Answer 1

This works for me:
--Construct sample data.
WITH FRED AS
(
SELECT 'A12' AS ID
, 1 AS TEST
UNION
SELECT 'A12' AS ID
, 2 AS TEST
UNION
SELECT 'A12' AS ID
, 3 AS TEST
UNION
SELECT 'A12' AS ID
, 5 AS TEST
UNION
SELECT 'A12' AS ID
, 8 AS TEST
UNION
SELECT 'B35' AS ID
, 1 AS TEST
UNION
SELECT 'B35' AS ID
, 3 AS TEST
),
--This is the sample data
test_data AS
(
SELECT *
FROM FRED F
ORDER BY ID, TEST
)
SELECT td.ID, td.TEST as RANGE1, MIN(td2.TEST) as RANGE2
FROM test_data td
cross join test_data td2
WHERE td.ID = td2.ID
AND
td.TEST < td2.TEST
GROUP BY td.ID, td.TEST
ORDER BY td.ID, td.TEST
test_data gives the sample you provided. I can try to handle repeated value cases once you let us all know how you want those to be handled. The current code above doesn't do that.

Answer 2

Assuming this is mysql (but most other DBMS will do the same) you can join the table with itself and use the limit in the ON clause.
Minima and grouping helps you from there.
e.g.:
mysql> SELECT m.id, m.test AS RANGE1 ,min(mm.test) AS RANGE2
FROM table1 AS m
INNER JOIN table1 AS mm ON m.id=mm.id AND mm.test > m.test
GROUP BY m.id,m.test;
+------+--------+--------+
| id | RANGE1 | RANGE2 |
+------+--------+--------+
| a12 | 1 | 2 |
| a12 | 2 | 3 |
| a12 | 3 | 5 |
| a12 | 5 | 8 |
| b35 | 1 | 3 |
+------+--------+--------+
5 rows in set (0.00 sec)
Take care with the efficiency of these things.
You might need to look into how to deal with edge cases where no second value is present in the table.
See also here: https://dba.stackexchange.com/questions/24014/how-do-i-get-the-current-and-next-greater-value-in-one-select