0<=>0 0.0<=>0.0 "A"<=>"A" NULL<=>NULL
1 1 1 1
1<=>0 0<=>NULL NULL<=>0
0 0 0
1.0<=>0.0 0.0<=>NULL NULL<=>0.0
"A"<=>"B" "A"<=>NULL NULL<=>"A"
id value id value t1.value<=>t2.value
1 NULL 1 NULL 1
id value
1 NULL
