Is there a function that can count unique values within a specific column accross multiple tabs in a spreadsheet and also count how many of each unique value there are?

I have multiple tabs in one sheet of clients and would like to find some way to count each unique item ( instance of a client name) from multiple tabs in a spread sheet. Also would like to be able to count how many of each unite client name there are. Further if it is possible to also have these results sorted by tab name and totaled would be awesome. If this is possible in libre office great, if not, I would simply love to know if there is a possibility for this and how to achieve it. This way I could know how many times any unique client name appears in the whole sheet, how many times in each individual tab and which one.

why is the data spread over multiple Sheets ??

I agree with @karolus, there has to be a really heavy reason why spread the data, you have over 1 million cells to use globally after all. Without something like a database backup in form of CSV/TSV you can’t just get that used that easily. In contrast, Google Sheets (new version) supports about 2 million cells globally.

Excuse my bad English. I did not understand the phrase “multiple tabs in one sheet” Did you mean “multiple tabs (sheets) in one workbook?”

Yes, such a function present at now. Try this example - CreateTableOfContents.ods