If the field contains 'yes'
or is blank, you can use a rollup with COUNTA(values)
for the aggregation function.
If the field contains 'yes'
, 'no'
, 'maybe'
, and so on (that is, if you’re looking for yesses among a number of possible results), you’ll need to define a formula field with the formula
IF({Query Field]='Yes',1,0)
and then roll up the values of that field using SUM(values)
as an aggregation function.