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Why does a many to one merge join change the sort order of the data set?

I have a query that calculates row_Number(). The table has a clustered index on the same columns (and order) as the partitioning and ordering for the row number. When using a merge join (many to one),...
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0answers
34 views

Are clustered indexes in Azure data warehouse ever a good idea on large tables?

Azure data warehouse supports both clustered and non-clustered indexes in addition to columnstore (which is the default for any new table). I know that having a large clustering key is normally ...
1
vote
1answer
31 views

How to index cube style queries with changing aggrigations

I've got a query that emulates the CUBE function. This is many different aggregations unioned together. select x,y,z, sum(a) from tbl group by x,y,z union all select x,'all',z, sum(a) from tbl group ...
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1answer
228 views

How can I obtain the full text for a query that appears in sys.dm_pdw_exec_requests?

I'm trying to tune a DB in Azure SQL Datawarehouse for queries produced by Power BI, which can connect directly to Azure SQL Data warehouse. I'm interested in studying execution plans, tweak things ...