Explanation:
Replace Data Source
Replace Data Source is a feature that allows you to replace one data source with another one that has the same or similar fields and structure. It updates all the worksheets that use the original data source with the new one, without reloading the data. In this case, you want to replace the data source that contains order data from 2019 with the one that contains order data from 2020.
To replace the data source, you need to do the following steps:
* Go to the Data Source tab at the bottom of the workbook to see the data source page. You will see a table that shows the fields and values from the original data source.
* Click on the drop-down arrow next to the data source name at the top of the page and select Replace Data Source from the menu. This will open a dialog box that allows you to replace your data source with another one.
* Select the data source that contains order data from 2020 from the list of available data sources and click OK. This will replace your original data source with the new one and update your worksheet accordingly. You may need to fix any broken fields or calculations that result from the replacement.
References: https://help.tableau.com/current/pro/desktop/en-us/datasource_replace.htm https://help.tableau.
com/current/pro/desktop/en-us/datasource_replace_workbook.htm

The LAST() function in Tableau returns the number of rows from the current row to the last row in the partition. When you compute using 'Order Date', it will change the partitioning of the calculation. If
'Consumer' in '2018' is the last row in its partition when computed by 'Order Date', then LAST() will return 0 for that cell.
The LAST() function in Tableau is a table calculation that returns the number of rows from the current row to the last row in the partition. The value of LAST() is 0 for the last row, increases by 1 for each row above the last row, and can be negative for rows below the current row if there are such rows in the partition.
In the provided visualization, LAST() is set to compute using Table (across). Changing the compute mode to use "Order Date" will adjust the partitioning of the data upon which the LAST() function is calculated. Since
"Order Date" is likely to be a unique value per row (assuming each order has a unique date), each row becomes its own partition.
For the Consumer segment of the year 2018, if "Order Date" is unique for each row, then the last row in each partition (in this case, each individual row) will have a LAST() value of 0 because there are no other rows in the partition - it's the last row of its own partition.
Therefore, when you change the compute mode of LAST() to use "Order Date", each cell under the Consumer segment for the year 2018 will have the LAST() value of 0, because each order date creates a partition of one, making every row the last in its partition.

Explanation:
There are different ways to create a table calculation that shows sales growth over each year, but one possible answer is:
* SUM([Sales])
* LOOKUP(SUM([Sales]), -1)
* PREVIOUS_VALUE(0)
To calculate the sales growth over each year, you need to compare the current year's sales with the previous year's sales and divide the difference by the previous year's sales. You can use the SUM, LOOKUP, and PREVIOUS_VALUE functions to achieve this. The SUM function returns the total sales for each year. The LOOKUP function returns the value of an expression in a target row, specified as a relative offset from the current row. The PREVIOUS_VALUE function returns the value of the expression in the previous row, or a specified value if there is no previous row. The formula for the table calculation is:
(SUM([Sales]) - LOOKUP(SUM([Sales]), -1)) / PREVIOUS_VALUE(0)
This formula subtracts the sales of the previous year (LOOKUP(SUM([Sales]), -1)) from the sales of the current year (SUM([Sales])) and divides the result by the sales of the previous year. If there is no previous year, the formula uses 0 as the denominator (PREVIOUS_VALUE(0)) to avoid division by zero errors.
References:
Tableau Certified Data Analyst Exam Prep Guide, page 11, section "Creating Calculated Fields" Tableau Help: SUM Function Tableau Help: LOOKUP Function Tableau Help: PREVIOUS_VALUE Function

To ensure that the data is updated every hour, you need to select Extract Refreshes from the data source menu on Tableau Server. This will allow you to add a new extract refresh schedule or edit an existing one. You can specify the frequency and time of the refresh, as well as any custom options or credentials. New will create a new data source, Connected Workbooks will show you which workbooks use this data source, and Connections will show you which tables or files are connected to this data source. References: https://help.
tableau.com/current/server/en-us/refresh_extracts.htm https://help.tableau.com/current/server/en-us
/refresh_extracts_add.htm
To ensure that the data is updated every hour on Tableau Server, you would need to go to the "Extract Refreshes" option. Here, you can schedule the data extracts to refresh at the desired frequency, which in this case would be every hour.