This will streamline your efforts without hunkering it down with all of the other SQL that Tableau generates without the custom SQL subquery. Use your SQL statements to create a view inside of the database, then connect that to Tableau. Rather than using custom SQL connections inside of Tableau Desktop, we suggest an alternative. Since Tableau can’t use Join Culling with custom SQL, this means every table gets hit on every query. When Join Culling is active, Tableau will only send a query to the necessary table(s) instead of all tables in the connection. Often times, for things like quick filters, Tableau will only be grabbing information from one table. Even though your SQL statement may run extremely efficiently on its own, when placed in a SQL subquery that is already burdened with other GROUP BY, ORDER BY, WHERE and more types of clauses, it can become cumbersome and slow quite quickly.īe very careful adding custom SQL connections, because the nature of a subquery means you’re not operating in a vacuum.Ĭustom SQL also prevents Tableau from using Join Culling. The reason that custom SQL connections can potentially cause a performance impact is that the SQL query is issued to the database inside of a subquery. Here are some insights on why limiting the amount of your custom SQL connections will create faster visualizations. Instead, it might actually be a significant impediment to your workbook’s performance. In other environments and in other tools, using your own custom SQL connections would be a way to improve and optimize performance. Where possible, create a view on the database server to implement your custom SQL and connect Tableau to your view. “Limit custom SQL in live connections as they can be inefficient. Each post expands upon one item listed in the master Tableau Performance Checklist. The Tableau Performance Checklist series is designed to help you streamline your dashboard performance and Tableau Server configuration.
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