Counting unique and group by from multiple spreadsheet

Question

I have problem in processing my data. I need to query unique ID from multiple sheets and group by specific criteria.

Here's the google sheet example so you can see the context

https://docs.google.com/spreadsheets/d/1Pudng2o1JjHpapFrxfciyZMRzodRRG9eroCl1yMb9vE/edit?usp=sharing

Looking forward for the help!

Answer 1

try:

=QUERY(UNIQUE({Sheet1!A2:B; Sheet2!A2:B; Sheet3!A2:B}), 
 "select Col2,count(Col2) 
  where Col2 is not null 
  group by Col2
  label count(Col2)''", 0)