Tableau Desktop's connection dialog has three options: (1) Single Table (2) Multiple Tables (3) Custom SQL. a nested select), and B) if you are going to use custom SQL, then you should also consider using our data extraction feature for performance reasons. Two best practices are to A) avoid custom SQL if at all possible, as we will generate a double-query for each drag and drop (one inside the other, i.e. If the Custom SQL is the basis for many different types of analysis, creating a view in the database is suggested, then connecting to it via the Single Tables option. For any of those needs, Custom SQL is the right choice. Tableau's Multiple Tables dialog does not currently have a method to create Sub-Selects, UNIONs, or ON clauses for filtering rather than relationships. However, there are cases where Custom SQL is necessary. Often this makes performance inferior to the queries produced automatically by VizQL against the basic Multiple Tables dialog (this will vary with the complexity of the query and the performance of the underlying database). With Custom SQL, Tableau will always use the provided query as the basis for all subsequent queries, as if the Custom SQL were a View in the database. Instead, you are encouraged to connect to the tables containing all of the data you need via the Multiple Tables dialog, then using filters and calculations within Tableau Desktop. Tableau's patented VizQL engine acts behind the scenes to translate your actions in Tableau into efficient SQL queries, so unlike many other tools, working with Tableau doesn't require that you write complex SQL query before beginning your analysis. Tableau aims to make connecting to and working with your data easy. Subject Area: Architecture Level of complexity: Advanced Approximate Time to complete: 1-2 hours Companion Workbook (twbx): n/a Additional Resources on the web: Reference Materials Toggle sub-navigation. Teams and Organizations Toggle sub-navigation.
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