What operation combines two records and displays them as one record in the querys result set?
Aggregate, join, or union your data to group or combine data for analysis. Show
Note: Starting in version 2020.4.1, you can now create and edit flows in Tableau Server and Tableau Online. The content in this topic applies to all platforms, unless specifically noted. For more information about authoring flows on the web, see Tableau Prep on the Web in the Tableau Server(Link opens in a new window) and Tableau Online(Link opens in a new window) help. Aggregate and group valuesSometimes you’ll need to adjust the granularity of some data, either to reduce the amount of data produced from the flow, or to align data with other data you might want to join or union together. For example, you might want to aggregate sales data by customer before joining a sales table with a customer table. If you need to adjust the granularity of your data, use the Aggregate option to create a step to aggregate or group data. Whether data is aggregated or grouped depends on the data type (string, number, or date).
Join your dataThe data that you want to analyze is often made up of a collection of tables that are related by specific fields. Joining is a method for combining the related data on those common fields. The result of combining data using a join is a table that’s typically extended horizontally by adding fields of data. Joining is an operation you can do anywhere in the flow. Joining early in a flow can help you understand your data sets and expose areas that need attention right away. Tableau Prep supports the following join types:
To create a join, do the following:
Inspect the results of the joinThe summary in the join profile shows metadata about the join to help you validate that the join includes the data you expect.
Common join issuesIf you don't see the results you expect after joining your data, you may need to do some additional cleaning on your field values. The following issues will result in Tableau Prep reading the values as not matching and exclude them from the join:
The good news is that if your field values have any of these issues, you can fix the field values directly in the Join Clauses or work with excluded values by clicking in the Excluded bars in the Summary of Join Results and use the cleaning operations in the profile card menu. For more information about the different cleaning options available in the Join step, see About cleaning operations(Link opens in a new window). Fix mismatched fields and moreYou can fix mismatched fields right in the join clause. Double-click or right-click the value and select Edit Value from the context menu on the field that you want to fix and enter a new value. Your data changes are tracked and added to the Changes pane right in the Join step.
You can also select multiple values to keep, exclude or filter in the Join Clauses panes, or apply other cleaning operations in the Join Results pane. Depending on which fields you change and where they are in the join process, your change is applied either before or after the join to give you the corrected results.
For more information about cleaning fields see Apply cleaning operations (Link opens in a new window). Union your dataUnion is a method for combining data by appending rows of one table onto another table. For example, you might want to add new transactions in one table to a list of past transactions in another table. Make sure the tables you union have the same number of fields, the same field names, and the fields are the same data type. Tip: To maximize performance a single union can have a maximum of 10 inputs. If you need to union more than 10 files or tables, try unioning files in the Input step. For more information about this type of union, see Union files and database tables in the Input step(Link opens in a new window). Similar to a join, you can use the union operation anywhere in the flow. To create a union, do the following:
Inspect the results of the unionAfter you create a union, inspect the results of the union to validate that the data in the union is what you expect. To validate your unioned data, check the following areas:
Fix fields that don’t matchWhen tables in a union don’t match, the union produces extra fields. The extra fields are valid data being excluded from their appropriate context. To resolve a field mismatch issue, you must merge the mismatched fields together. There are a number of reasons why fields might not match.
Additional merge field optionsIn addition to the methods described in the above section for merging fields you can also use one of the following methods to merge fields. You can merge fields in any step, except for the Output step. For information about how to merge fields in the same file, see Merge fields. To merge fields, do one of the following:
How do you combine the results of two queries?The UNION operator is used to combine the result-set of two or more SELECT statements.. Every SELECT statement within UNION must have the same number of columns.. The columns must also have similar data types.. The columns in every SELECT statement must also be in the same order.. Which operators combine the results of two or more component queries into one result?Set operators combine the results of two component queries into a single result. Queries containing set operators are called compound queries. Table 4-4 lists SQL set operators.
Which set operator is used to combine the result sets of two or more queries into a single result set?The UNION operator is used to combine the data from the result of two or more SELECT command queries into a single distinct result set. This operator removes any duplicates present in the results being combined.
Which operator is used to find the result of two queries?The SQL INTERSECT operator is used to return the results of 2 or more SELECT statements. However, it only returns the rows selected by all queries or data sets.
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