To apply a custom data role to a field, you need to select the data type of the field and then choose the data role from the list of available roles. This will validate the values in the field against the data role and mark any invalid values with a red exclamation mark. To fix the invalid values, you can use the Group Values option and select the Spelling algorithm, which will group values that are close in spelling and replace them with the most frequent value in the group. This will help you standardize the values in the Material field and match them with the Role1 data role. Reference: The information is based on the following sources:
Use Data Roles to Validate your Data - Tableau
New in Tableau Prep: Automatically identify data quality issues with Data Roles

To combine the two tables that contain data about books in a library and ensure that all the data is retained, you should use a full outer join. A full outer join is a type of join that returns all rows from both tables, regardless of whether there is a match or not. If there is no match, null values are filled in for the missing fields.
To perform a full outer join, you need to do the following steps:
* Connect to both tables as your data sources in Tableau. You can use either live or extract connections.
* Drag one table to the canvas and drop it on top of another table. This will create a join between them based on a common field.
* Click on the join icon between the tables and select Full Outer Join from the drop-down list. This will change the join type to full outer join and show all rows from both tables.
* Optionally, you can add or remove join clauses by clicking on Add or Remove buttons next to each clause. You can also change or rename fields by clicking on them.
The other types of joins are not correct for this scenario. An inner join returns only the rows that have a match in both tables, which will exclude any books that are missing from either table. A left join returns all rows from the left table and only the matching rows from the right table, which will exclude any books that are only in the right table. A right join returns all rows from the right table and only the matching rows from the left table, which will exclude any books that are only in the left table. References: https://help.tableau.com
/current/pro/desktop/en-us/joining_tables.htm https://help.tableau.com/current/pro/desktop/en-us/join_types.
htm
When combining two datasets that are both incomplete and where it's important to retain all data from both sources, a full outer join is appropriate. This type of join ensures that all records from both tables are included in the combined dataset, even if there are no matching records in the other table.

Using relationships: You can use relationships to link the secondary data source with the primary data source based on a common field. This will allow you to use fields from both data sources in your visualization without creating new fields or duplicating data. You can then replace references to update the dimension values. For example, you can use relationships to link the updated dorm codes with the primary data source and then replace Dorm_Code with Dorm_Code_New in your visualization.
https://community.tableau.com/s/question/0D54T00000C5ldZSAR/update-data-view-based-on-dimension To update existing visualizations with new codes without changing the field name, using relationships to bring in the secondary data source is appropriate. Then using Replace References allows you to update the references from the old dorm codes to the new ones while maintaining the existing field name.

Explanation:

To customize a layout for mobile users, you should select the Device Preview option first. This option will allow you to see how your dashboard will look on different types of devices, such as phones, tablets, or desktops. You can also choose different models and orientations to preview different screen sizes and resolutions. From the Device Preview mode, you can add, edit, or delete device layouts for each device type.
You can also adjust the size, position, and formatting of the dashboard elements for each device layout. References:
Create Dashboard Layouts for Different Device Types - Tableau
Tableau Certified Data Analyst Study Guide