Count NULL and other values in tableau

I'm new to Tableau, so I've only been able to solve your problem partly -

1. In Rows Shelf, add your Field_Name.
2. In Marks Card, double click to create a fresh criteria, and enter text - COUNT([Field_Name])
3. Choose category of the criteria as Text instead of Details

This creates a list of unique items in your List and their counts; except for the Null values (My dataset contains 2 Null entries).
Note: The counts of the null values can be checked by clicking the Null 0 row, and selecting the Full Data tab from View Data...

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Upon digging into Tableau fundamentals, I learnt that you can do this with 2 simple steps:-

1. You may place the attribute in Row Shelf.
2. In the Navigation Panel on the left, under Measures section, you'll find something called Number of Records OR ExcelWorksheetName (Count) in italics. Drag that into the Data area of the visualization.

This approach gives you the Null counts as well! :)

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