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.

1 - Add the date to the Columns shelf. Add the segment and the sales to the Rows shelf.
2 - Aggregate the date to month and year.
3 - From the Analytics pane, drag Forecast to the worksheet.

Explanation:
Select
Where
The correct way to complete the query is:
SELECT * FROM [dbo] . [Students]
WHERE [Students].[City] = 'Berlin'
The SELECT statement is used to retrieve data from a table or a view. The * symbol means that all columns will be returned. The FROM clause specifies the table or view name and the schema name.
The WHERE clause is used to filter the data based on a condition. The condition is [Students].[City] =
'Berlin', which means that only rows where the City column of the Students table is equal to 'Berlin' will be returned.
The other options are not relevant for this query. CAST is a function that converts a value from one data type to another. JOIN is a clause that combines data from two or more tables based on a common field. ON is a keyword that specifies the join condition. UNION is a set operation that combines the results of two or more queries into one result set.
References: https://docs.microsoft.com/en-us/sql/t-sql/queries/select-transact-sql?view=sql-server-ver15
https://docs.microsoft.com/en-us/sql/t-sql/queries/where-transact-sql?view=sql-server-ver15
https://docs.microsoft.com/en-us/sql/t-sql/functions/cast-and-convert-transact-sql?view=sql-server-ver15
https://docs.microsoft.com/en-us/sql/t-sql/queries/from-transact-sql?view=sql-server-ver15#join
https://docs.microsoft.com/en-us/sql/t-sql/language-elements/set-operators-union-transact-sql?view=sql-server-v

To group all five names automatically, you should use Manual Selection as a grouping option in Tableau Prep. Manual Selection is a feature that allows you to select values from your data and group them together based on your criteria. You can use Manual Selection by clicking on Group Values in Profile pane > Manual Selection from the menu. This will open a dialog box where you can select values from your data and assign them to a group.
In this case, you want to group all five names together based on their spelling variations. You can use Manual Selection by selecting all five values from your data and assigning them to a group named "Harry Potter". This will create a new field named Grouped Field that contains "Harry Potter" as one value.
The other options are not correct for this scenario. Pronunciation is a feature that groups values based on how they sound, but it may not work well with names or uncommon words. Spelling is a feature that groups values based on common spelling errors or typos, but it may not recognize all variations or synonyms. Common Characters is a feature that groups values based on the number of characters they share, but it may not capture the meaning or context of the values. Reference: https://help.tableau.com/current/prep/en-us/prep_group.htm https://help.tableau.com/current/prep/en-us/prep_group_manual.htm