162
162
insert into t1 values (7,null), (8,null), (8,7);
163
163
explain select * from t1 where a = 7 and (b=7 or b is null);
164
164
id select_type table type possible_keys key key_len ref rows Extra
166
166
select * from t1 where a = 7 and (b=7 or b is null);