Symptom
During migration project, customer found legacy 'Union All' query returned incorrect result.
Latest patch SP10.7 has a fix related to 'Union all' issue. But this query still returned incorrect result in IQ16 SP10.7.
* SQL structure and Findings :
- Only 'Block-A' returns 88 rows
- Only 'Block-B' returns 0 rows
- But whole SQL should return 88 rows. But 0 rows returns.
- Using Options, Dml_options7=8 or Join_preferemce=-4, returns 88 rows.
Select-Block-A --- return 88 rows
UNION ALL
Select-Block-B --- return 0 rows
( B-1
UNION ALL
B-2
) A
LEFT OUTER JOIN ( B-3 )
LEFT OUTER JOIN ( B-4 )
LEFT OUTER JOIN ( B-5 )
... ;
* W/A : Below two W/A each makes correct results
1) SET temporary option Dml_options7=8
2) SET temporary option Join_preferemce=-4 ; -- avoid hash join
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Environment
SAP IQ 16.0
Product
Keywords
"parallel outer algorithm" ; "serial outer join algorithm" ; , KBA , BC-SYB-IQ , Sybase IQ , Problem
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