Teradata - to solve a data issue with query or Procedure

Question

I am new to Teradata. I have to solve below problem using SQL/Stored procedure in Teradata.

Problem - As shown in below input data, We need to link the records in the table by the values of Col1 and Col2.

Logic - For all set of records which are having linking values of col1 and col2 should have min(col1) as col3.

for example row 1-5 are linked by 3160370 and 4856938 values and hence should have 3160370 in col3.

Input data

    Col1    Col2
1   3160370 3160370
2   3160370 4856938
3   3160370 11633062
4   4856938 11633063
5   4856938 11633064
6   4271481 4271481
7   4271481 5968049
8   4271481 12744173
9   5968049 12744174
10  5968049 12744175

Output data

    Col1    Col2        Col3
1   3160370 3160370     3160370
2   3160370 4856938     3160370
3   3160370 11633062    3160370
4   4856938 11633063    3160370
5   4856938 11633064    3160370
6   4271481 4271481     4271481
7   4271481 5968049     4271481
8   4271481 12744173    4271481
9   5968049 12744174    4271481
10  5968049 12744175    4271481

Please let me know if more details are needed to solve this problem.

Please help!

Answer 1

This is a simple task for recursion:

WITH RECURSIVE cte (Col1, Col2, minCol) AS
 (
   SELECT Col1, Col2, Col1 AS minCol
   FROM   tab
   WHERE  Col1 = Col2

   UNION ALL

   SELECT t.Col1, t.Col2, cte.minCol
   FROM   cte JOIN tab AS t
   ON  cte.Col2 = t.Col1
   AND t.Col1 <> t.Col2
 )
SELECT * FROM cte

Of course it's more complicated if there are any loops in your data...