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Soumitra Sengupta wrote:
> This is one of those few times I agree with Dare :-)) even though we
> work for the same company. He points out one of the big challenges.
> Couple of comments:
> If we are querying over a bunch of back-end relational databases, why is
> XQuery better than some flavor of SQL? At least the type system
> mismatch could be manageable.
It isn't better. The only reason I can think of to use XQuery in this
situation is that you want to construct reasonably complex XML from the
results, and even then you need to make some trade-offs. SQL will almost
certainly be faster but require post-processing to construct the XML;
XQuery will be easier to write.
XQuery is useful as a data integration language when the data sources do
not easily map to relational.
> Honestly, whether we use a SQL DQP or XQuery DQP is not the biggest
> problem. Semantic and structural mismatches, data quality, policies
> around running arbitrary queries on mission critical data stores, data
> volume, updates, security and access control and metadata management are
> the bigger problems.