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Introductie van Micorosoft SQL Server 2016

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188 C H A P T E R 9 | Introducing Azure SQL Data Warehouse Note To learn more about using ADF to execute a stored procedure in SQL Data Warehouse, see "SQL Server Stored Procedure Activity" at us/documentation/articles/data-factory-stored-proc-activity/. Using PolyBase Another option for loading data into SQL Data Warehouse is PolyBase, a SQL Server feature that we describe in Chapter 5, "Broader data access." You can use it to query text or CSV files or nonrelational data stored in Hadoop or blob storage and join the data queried to query results from your data warehouse. You can also use PolyBase to migrate data from one of these storage types into the data warehouse. To do this, PolyBase uses external tables that you define in the SQL Data Warehouse and then allows you to query these tables by using T-SQL. Compared to other options, PolyBase is the fastest and most scalable of the loading methods. In addition, PolyBase automatically parallelizes the data-load process, thereby eliminating the need to explicitly create subsets of your data for multiple data loads that you run concurrently. Nonetheless, the use of PolyBase still requires some new development for your workloads as we describe later in this section. However, the load speed is fast because PolyBase bypasses the control node and loads data directly to the data nodes, as shown in Figure 9-6. The other load methods that we discuss in this chapter cannot access the data nodes directly and consequently run more slowly. Figure 9-6: Parallel loading of SQL Data Warehouse from Azure Blob Storage. As an example of using PolyBase for data loading, let's assume that you want to add new sales territories from blob storage into your data warehouse. The data is currently in a comma-delimited text file named dimsalesterritory.txt, which looks like this: 11,Netherlands,Netherlands,Europe 12,Denmark,Denmark,Europe Navigate to the storage account blade into which you want to copy the text file, and then click the Blobs tile. Take note of the blob-service endpoint in the Essentials section of the Blob Service blade. Then, in the storage account blade, click the Settings button, and then click Access Keys in the

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