As expected, the data resulting from the join is now available for review in the Profile Pane, and the column headers are color-coded to match. In many databases, such as Exasol, this enforces a materialization of the result, which has a positive effect on the performance of repetitive queries. Do this by dragging and dropping from the Flow Pane onto the New Join side of sales1: Looking at the Join Panel in the Profile Pane, Tableau Prep smartly recognizes the join will be on CustomerID. If you use the same query in a source several times (to query all history objects, for example), it is worth writing this as a custom query and adding an "order by false" to it at the end.
The settings stop the Tableau Engine from carrying out unnecessary grouping and aggregation and this improves the performance of queries. "All records match" is better than "some records match". Environment Tableau Prep Resolution As a workaround, in Tableau Prep, open the desired flow from within the Tableau Prep interface, via a thumbnail, or the Open dialog in the menu. "Many-to-one" is preferable to "many-to-many". tfl file that contains Custom SQL, Tableau Prep hangs on the splash screen (becomes unresponsive) and will not open. The general rule here is: the more precise, the better. Performance options is another feature in Tableau 2020.2 that can be set in the relationships between tables, allowing the developer to optimize the generated SQL queries. This makes the generated SQL queries much leaner. Thanks to the logical level introduced in Tableau 2020.2, only those objects are queried t hat are actually needed. You can further customize the exact OData data pulled by Using Custom SQL. Prior to version 2020.2, the Tableau Engine always queried all the tables connected in the data source even if only a small percentage of the tables were actually needed in the workbook. The connector supports Tableau Desktop 2020.1 or later and Tableau Prep. These depend mainly on the operations in the workbook and are generated dynamically by the Tableau Engine.
The source developer can exert only a limited influence over the SQL queries generated by Tableau.
Switching to "logical data source" available in Tableau from version 2020.2
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