[teiid-issues] [JBoss JIRA] (TEIID-4133) SQL Server requires CAST when using NULL in anchor part of recursive CTE

[Andrej Šmigala (JIRA)]

Andrej Šmigala created TEIID-4133:
-------------------------------------

             Summary: SQL Server requires CAST when using NULL in anchor part of recursive CTE
                 Key: TEIID-4133
                 URL: https://issues.jboss.org/browse/TEIID-4133
             Project: Teiid
          Issue Type: Bug
          Components: JDBC Connector
    Affects Versions: 8.12.x
            Reporter: Andrej Šmigala
            Assignee: Steven Hawkins


Running the following query in teiid:
{code:sql}
with a (intkey, stringcolumn, lvl) as
    (
    select intkey, NULL as stringcolumn, 0 as lvl from bqt1.smallb where intkey = 1
    union all 
    select n.intkey, n.stringkey as stringcolumn, rcte.lvl + 1 as lvl from bqt1.smallb n inner join a rcte on n.intkey = rcte.intkey + 1
    )
 select * from a
{code}

results in the following source query:
{code:sql}
WITH a (intkey, stringcolumn, lvl) AS
    (
    SELECT SmallB.IntKey, NULL AS stringcolumn, 0 AS lvl FROM SmallB WHERE SmallB.IntKey = 1
    UNION ALL
    SELECT n.IntKey, n.StringKey AS stringcolumn, (rcte.lvl + 1) AS lvl FROM SmallB n INNER JOIN a rcte ON n.IntKey = (rcte.intkey + 1)
    )
SELECT a.intkey, a.stringcolumn, a.lvl FROM a
{code}

which fails on SQL Server with {noformat}Types don't match between the anchor and the recursive part in column "stringcolumn" of recursive query "a".{noformat}.

The source query should be 
{code:sql}
WITH a (intkey, stringcolumn, lvl) AS
    (
    SELECT SmallB.IntKey, CAST(NULL AS VARCHAR(10)) AS stringcolumn, 0 AS lvl FROM SmallB WHERE SmallB.IntKey = 1
    UNION ALL
    SELECT n.IntKey, n.StringKey AS stringcolumn, (rcte.lvl + 1) AS lvl FROM SmallB n INNER JOIN a rcte ON n.IntKey = (rcte.intkey + 1)
    )
SELECT a.intkey, a.stringcolumn, a.lvl FROM a
{code}

i.e. the NULL has to be cast to the precise type of the column in the recursive part of the query.



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