#f in ('a')
f = 'a'
f != 'a'
f > 'a'
f < 'a'
f >= 'a'
f <= 'a'
f is TRUE
f is FALSE
f is NULL
f > 'a' and false
false and f > 'a'
f < 'a' or f > 'b' or f > 'sda' and f > 'sds' or f = 'adas'
f > 'a' or f > 'b' and (g > 'a' or g > 'k') and (f > 'c')
f > 'a' and g > 'a' and h > 'a' and i > 'a' and j > 'a'
f > 'a' and f < 'B' 
f > 'B' and f < 'a' and g > 'a' and g < 'b'
f > 'B' or f < 'a' and g > 'a' or g < 'b'
f > 'B' and f < 'a' and g > 'a' and g < 'B'
f > 'B' and 'a' = 'A'
#(f, g) in (('a', 'b'), ('B', 'A'))
#(f, g) > ('a', 'b') and (f, g) < ('B', 'A')
f between 'a' and 'b'
f between 'B' and 'a'
f not between 'a' and 'b'
f = 'a' + 'b'