This type of error is generated when we add left expect left hand side of the expression to be evaluated but we have not specified the right hand side variable on which the value will be checked.
For example:
while querying the databse if the query is like:
" Select * from user where id = 1 and = 'asad' "
Here i have specified the right side of first filter as id but the right side of 'asad which should be name in this case is missing and thus the error of non-Boolean type expression will occur here.
