17.10 - Example: Left Outer Join Usage - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Definition Language Syntax and Examples

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
Publication ID
B035-1144-171K
Language
English (United States)

The first recursive view definition demonstrates a correct use of a left outer join, which is highlighted in bold. The usage is valid because the recursive relation in the recursive statement of the view definition is used as the outer relation in the left outer join.

    CREATE RECURSIVE VIEW rec (f1, mycount) AS (
      SELECT a1, 0 AS mycount
      FROM nonrec
    UNION ALL
      SELECT a2, mycount + 1
      FROM  rec LEFT OUTER JOIN nonrec ON nonrec.a1 = rec.f1 
      WHERE rec.mycount <= 100);

The second recursive view definition demonstrates a non-valid use of a left outer join, which is highlighted in bold. The usage is not valid because the recursive relation in the recursive statement of the view definition is used as the inner relation in the left outer join.

    CREATE RECURSIVE VIEW rec (f1, mycount) AS (
      SELECT a1, 0 AS mycount
      FROM nonrec
    UNION ALL
      SELECT a2, mycount + 1
      FROM  nonrec LEFT OUTER JOIN rec ON nonrec.a1 = rec.f1 
      WHERE rec.mycount <= 100);

You can use left outer joins without restriction in the seed statement of a recursive view definition.