159
162
insert into t1 values (7,null), (8,null), (8,7);
160
163
explain select * from t1 where a = 7 and (b=7 or b is null);
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164
id select_type table type possible_keys key key_len ref rows Extra
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166
select * from t1 where a = 7 and (b=7 or b is null);