Google Sheet Query Error: Unable to parse query string for Function QUERY parameter 2: AVG_SUM_ONLY_NUMERIC

Question

I am getting this error message on my query formula

"Unable to parse query string for Function QUERY parameter 2: AVG_SUM_ONLY_NUMERIC"

and I don't know what seems to be the problem. I already change the format of column C to percentage but I'm still getting the same error.

=Query('Sheet1'!A1:C, "select A, avg(C), count(C) group by A,C", 1)

Sample Data:

 Date      | Name | CSAT %|
-----------|------|-------|
 2017-10-22| asdf |   100%|
 2017-10-15| qwer |   50% |
 2017-10-08| zxcv |   75% |
 2017-10-01| qwer |   90% |

Answer 1

One column of numerical data in my sheet would not register as numbers, no matter what (you can test this with function N(). It will show 0 for data which isn't considered numerical).

I fixed this with an extra column which added 0 to my numerical column. Even though the original column wasn't considered numerical, this somehow worked.

Answer 2

I finally solved the puzzle using this:

=arrayformula(query({'Sheet1'!A:N, arrayformula(if(ISBLANK('Sheet1'!O:O), -1, value('Sheet1'!O:O)))

Basically, I put -1 on blank spaces in between rows and then on my query, I placed a condition to include only rows that have a value of >=0.