Elastic Query in Azure SQL Database and Views
Creating views that join across databases? Read this article to find out how to make those views play nice with Elastic Query.
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The question came up: How do the constructs necessary for Elastic Query within Azure SQL Database affect your ability to create views that join across databases? Since I haven’t tested this myself, and I haven’t seen anyone else doing anything with it yet, I decided to set up a test. I recreated my cross database queries using the scripts posted here. Let’s create a view:
CREATE VIEW dbo.JoinedView AS SELECT dt.Val, dt2.Val AS Val2 FROM dbo.DB1Table AS dt LEFT JOIN dbo.DB2Table AS dt2 ON dt2.ID = dt.ID;
If I run the query, I get back results. Done. We can create views that join between Azure SQL Databases… But, views are all about masking right? What if I wanted to change the name of the table in my database. Could I do something like this?
CREATE EXTERNAL TABLE dbo.CanICheatThisName ( ID int, Val varchar(50)) WITH ( DATA_SOURCE = DB2Access);
The CREATE script runs just fine with no errors. When I try to query it, though:
Msg 46823, Level 16, State 2, Line 55
Error retrieving data from one or more shards. The underlying error message received was: ‘Invalid object name ‘dbo.CanICheatThisName’.’.
Understanding how the Elastic Query works, of course this fails. So… what about faking it the other way? I’ll create a view in my second database:
CREATE VIEW dbo.FakeTable AS SELECT * FROM dbo.DB2Table AS dt;
Now, I’ll create the EXTERNAL TABLE using the name of the view:
CREATE EXTERNAL TABLE dbo.FakeTable ( ID int, Val varchar(50)) WITH ( DATA_SOURCE = DB2Access);
When I query this, the data comes across just fine.
Creating a view, or any other query, that joins across databases using Elastic Query works just fine. However, if you want to mask things using a view, you might need to get a little creative in how you implement Elastic Query. The good news is, Elastic Query is somewhat, shall we say, elastic in how you set it up. More so than it immediately appears.
Published at DZone with permission of Grant Fritchey, DZone MVB. See the original article here.
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