Working with Tables in Azure SQL Data Warehouse

  • ctesta-oneill

    SSC Veteran

    Points: 203

    Comments posted to this topic are about the item Working with Tables in Azure SQL Data Warehouse

  • xsevensinzx

    One Orange Chip

    Points: 25558

    Thanks for the article.

    Just to emphasize the Hash table section some more. There is only 60 distributions that your Hashed key will be stored in. That means you should at least have 60 unique values or more with the column of data you choose to hash on in a deterministic fashion. 

    As mentioned in the article, if you have a lot of default values or NULLs in that particular field, then you may want to consider another column or blend those defaults in some manner that can evenly be distributed across those 60 distributions. In the event you ignore the default value, then you can end up with one database of the 60 with all the values for that particular default value. Thus, if you ever query it, then you end up with one database doing all the work within the compute node versus distributing the compute across the other nodes.'

  • Rolf Tesmer (Mr. Fox SQL)

    SSC Enthusiast

    Points: 160

    Also worth mentioning that REPLICATED table support is coming, which will bring the ASDW PaaS service more closely in line with APS (on-prem).
    https://feedback.azure.com/forums/307516-sql-data-warehouse/suggestions/10638774-replicated-table-support

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    Rolf Tesmer (Mr. Fox SQL)
    https://mrfoxsql.wordpress.com/
    rolf.tesmer@mrfoxsql.com.au
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