When you use data blending to combine your data from different data sources, there are a few common issues that might arise. This topic lists them and describes how you can respond to each situation. Show
Common warnings and errors when blending data sourcesNo relationship to the primary data sourceWhen you drag a field from a secondary data source to the view, you might see a warning that says: Fields cannot be used from the [name of secondary data source] data source, because there is no blend relationship to the primary data source. In the Data pane, switch to the [name of secondary data source] data source, and click at least one link icon to blend these data sources. This warning occurs when you have no active links in the secondary data source For example, suppose you have two data sources that are related by the State and Date fields. At least one of these fields must have the active link icon ( ) next to it in the secondary data source. You can make the link active by clicking the link icon in the Data pane or by using the linking field from the primary data source in the view.The secondary data source may not have any links to the primary data source. Look in the Data pane for the link icon. Tableau automatically links fields that have the same name. If your fields do not have the same name, you must define a link between them. For more information, see Blend Your Data. Primary and secondary connections are from tables in the same data sourceWhen you drag a field from a secondary data source to the view, you might see a warning that says: The primary and secondary connections are from tables in the same data source. Instead of linking the connections, use the Data menu to join the data. Joins can integrate data from many tables and may improve performance and filtering. This warning occurs when the workbook contains separate data sources that connect to the same database. Though you can combine data in this way, Tableau recommends that you use a join or relationship to combine data from the same database instead, as they can leverage some of the database’s native optimizations in ways blending can’t. Cannot blend the secondary data source because one or more fields use an unsupported aggregationData blending has some limitations regarding non-additive aggregates such as COUNTD, MEDIAN, and RAWSQLAGG. Non-additive aggregates are aggregate functions that produce results that cannot be aggregated along a dimension. Instead, the values have to be calculated individually. All Number functions, except for MAX and MIN, are non-additive aggregates. For more information, see Tableau Functions (by Category). These limitations cause certain fields in the view to become invalid under certain circumstances. If you hover your mouse cursor over one of these invalid fields, you see the following error: Cannot blend the secondary data source because one or more fields use an unsupported aggregation.
This error can occur for one of the following reasons:
Data sources that contain logical tables cannot be used as secondary data sources for data blendingThe secondary data source can use logical joins as long as the following conditions are satisfied:
Asterisks show in the sheetWhen you blend data, make sure that there is only one matching value in the secondary data source for each mark in the primary data source. If there are multiple matching values, you see an asterisk in the view that results after you blend data. For example, suppose you have two data sources: Population and Superstore. The primary data source, Population, has a field called State. The secondary data source, Superstore, contains fields called State and Segment. In the secondary data source, each state has multiple segments. Alabama, for example, has three segments: Consumer, Corporate, and Home Office.
When you blend the two data sources on the State field, you create a link where individual state values (in the primary data source) can have multiple segment values (in the secondary data source). In this case, multiple values for segments in the secondary data source for each corresponding state value in the primary data source cause asterisks to appear in the view, as demonstrated by the images below. Blended data
Resolve asterisks in the sheetAvoid asterisks in the sheet by making sure that there is only one matching value in the secondary data source for each mark in the primary data source. Though the way you ensure this depends on the data and the view you're trying to create, consider one of the following suggestions to resolve asterisks in the sheet.
Null values appear after blending data sourcesNull values can sometimes appear in place of the data you want in the view when you use data blending. Null values can appears for a few reasons:
Data blending works by supplementing the data in the primary data source with data from the secondary data source based on the linking field. This means Tableau takes all the data in the primary data source, and only the corresponding matches in the secondary data source. If Tableau cannot identify at least one matching value in the secondary data source for the corresponding value in the primary data source, null values appear. You can resolve this issue by doing the following:
Blending issues after publishing data sourcesWhen you make a field-level customization that blends two data sources, the customization is based on one of the data sources, the primary data source. Then, when the primary and secondary data sources are published to Tableau Server or Tableau Cloud, the primary data source, which contains the customization (i.e., the reference to the secondary data source) no longer works. The customization no longer works because the blend relationship between the primary and secondary data sources is lost. This is because the blend relationship between the primary and secondary data sources is defined at the workbook level. For example, suppose you have two data sources: Store - Main and Store - West. You create a field-level customization, like a calculation, that combines the sales totals from the primary data source, Store - Main, with the sales totals from the secondary data source, Store - West. As soon as you publish the data sources to Tableau Server or Tableau Cloud, the calculation in Store - Main no longer works. This is because the calculation refers to the secondary data source, Store - West, whose location is now undetermined. To work around this scenario, do the following:
Blending with a cube (multidimensional) data sourceCube data sources can only be used as the primary data source for blending data in Tableau. They cannot be used as secondary data sources. Other data blending issuesFor other issues that emerge while blending data, see the following links. Sort is not available
Which of the following is an advantage of secondary data over primary data?Advantages of Secondary data
It is economical. It saves efforts and expenses. It is time saving. It helps to make primary data collection more specific since with the help of secondary data, we are able to make out what are the gaps and deficiencies and what additional information needs to be collected.
What is the main advantage of secondary research data over primary research data?One of the most noticeable advantages of using secondary data analysis is its cost effectiveness. Because someone else has already collected the data, the researcher does not need to invest any money, time, or effort into the data collection stages of his or her study.
What are the advantages of secondary data quizlet?The chief advantage of secondary data is availability, meaning they are almost always less expensive to obtain and faster to obtain than primary data. Often, researchers use sec- ondary data when relevant primary data are impossible or impractical to obtain.
What are the advantages of secondary research?Advantages of Secondary Research
Secondary data can be faster and cheaper to obtain, depending on the sources you use. Secondary research can help to: Answer certain research questions and test some hypotheses. Formulate an appropriate research design (e.g., identify key variables).
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