IQ currently provides somewhat different support for subqueries from Adaptive Server Enterprise and Adaptive Server Anywhere.
Adaptive Server Enterprise and Adaptive Server Anywhere support subqueries in the ON clause; IQ does not currently support this.
UNION in subqueries is supported as follows:
Adaptive Server Anywhere supports UNION in both correlated and uncorrelated subqueries.
IQ only supports UNION in uncorrelated subqueries.
Adaptive Server Enterprise does not support UNION in any subqueries.
Adaptive Server Anywhere supports subqueries in many additional places that a scalar value may appear in the grammar. Adaptive Server Enterprise and IQ follow the ANSI standard in where subqueries may be specified.
