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SQL queries ran on native Data source in VDP

Hello there, I just a few questions, I was wondering if you could provide me with an answer. How can I edit a SQL query that I created directly on the Data Source(Hadoop)? How should the SQL query be written, names the datasource, table, and fields in Data Source? What are the tradeoffs between running an SQL query directly on Data Source(Hadoop) to create a base view and running VQL to create a base directly on VDP? What is the performance for these two instances? Sorry for the questions, I just think this crucial to understanding the tradeoffs between running queries on Denodo or at a Native Data Source. Thanks in advance.
user
24-08-2017 09:31:49 -0400

1 Answer

Hi In the base view of Virtual DataPort, you could apply the schema changes made in the data source, by clicking on “Source Refresh” in the edit tab of the base view. Refer this [link](https://community.denodo.com/docs/html/browse/6.0/vdp/administration/creating_views/importing_data_sources_and_creating_base_views/source_refresh#source-refresh) for more details. You could follow the naming convention details given in the Knowledge Base article [VDP Naming Conventions](https://community.denodo.com/kb/view/document/VDP Naming Conventions?category=Operation), while you create a view, data source, webservices in Virtual DataPort. Virtual DataPort uses VQL, which is a SQL like language, you could refer the Knowledge Base article [VDP Conformance with Standard SQL](https://community.denodo.com/kb/view/document/VDP Conformance with Standard SQL?category=VQL) for more details. In a JDBC/ODBC data source you could create the base views using the options “Create selected” and “Create from query”, Choosing “Create selected”, an element tree would be listed consisting of tables, views, stored procedure in the database and you could choose the required elements to create the base view. When the created base view is executed the query would be delegated to the data source, refer this [link](https://community.denodo.com/docs/html/browse/6.0/vdp/administration/creating_views/importing_data_sources_and_creating_base_views/jdbc_sources#creating-base-views-from-a-jdbc-data-source) for more details. When the base view created using the option “Create from query”, you would not have the benefit of tree view, used by, data lineage and propagation of changes functionalities among the tables used in the SQL Sentence. You could refer the knowledge base article [Using the Create Base View From Query Option](https://community.denodo.com/kb/view/document/Using the Create Base View From Query Option?category=Data+Sources) for more details on the limitations of using it. Hope this helps!
Denodo Team
29-08-2017 10:30:36 -0400
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