>I have a header table that has two one-to-many relationships to 2 independent detail tables. I would need to generate a report that displays header information and then a subreport for each table filtered to the Header Id.
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>Is SSRS a alternative at all? It seems incredibly slow.
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>Thanks for any suggestion on how to approach this, other than coding this generating a rather convoluted Excel worksheet.

SSRS subreports can be slow, especially if they have to iterate over a large number of rows. If you can imagine how a DBA fears what a correlated subquery did in SQL Server 15 years ago, that's how SSRS processes subreports today

My only advice - if subreports are going to slow things down unacceptably, you might consider exploding the original result set as one big matrix/Cartesian product. Yes, that can present challenges in the report designer, depending on the output requirements.