# # Check null keys drop table if exists t1; create table t1 (a int, b int not null,unique key (a,b),index(b)) type=myisam; insert ignore into t1 values (1,1),(2,2),(3,3),(4,4),(5,5),(6,6),(null,7),(9,9),(8,8),(7,7),(null,9),(null,9),(6,6); explain select * from t1 where a is null; explain select * from t1 where a is null and b = 2; explain select * from t1 where a is null and b = 7; explain select * from t1 where a=2 and b = 2; explain select * from t1 where a<=>b limit 2; explain select * from t1 where (a is null or a > 0 and a < 3) and b < 5 limit 3; explain select * from t1 where (a is null or a = 7) and b=7; explain select * from t1 where (a is null and b>a) or a is null and b=7 limit 2; explain select * from t1 where a is null and b=9 or a is null and b=7 limit 3; explain select * from t1 where a > 1 and a < 3 limit 1; explain select * from t1 where a > 8 and a < 9; select * from t1 where a is null; select * from t1 where a is null and b = 7; select * from t1 where a<=>b limit 2; select * from t1 where (a is null or a > 0 and a < 3) and b < 5 limit 3; select * from t1 where (a is null or a > 0 and a < 3) and b > 7 limit 3; select * from t1 where (a is null or a = 7) and b=7; select * from t1 where a is null and b=9 or a is null and b=7 limit 3; alter table t1 modify b blob not null, add c int not null, drop key a, add unique key (a,b(20),c), drop key b, add key (b(10)); explain select * from t1 where a is null and b = 2; explain select * from t1 where a is null and b = 2 and c=0; explain select * from t1 where a is null and b = 7 and c=0; explain select * from t1 where a=2 and b = 2; explain select * from t1 where a<=>b limit 2; explain select * from t1 where (a is null or a > 0 and a < 3) and b < 5 and c=0 limit 3; explain select * from t1 where (a is null or a = 7) and b=7 and c=0; explain select * from t1 where (a is null and b>a) or a is null and b=7 limit 2; explain select * from t1 where a is null and b=9 or a is null and b=7 limit 3; explain select * from t1 where a > 1 and a < 3 limit 1; explain select * from t1 where a is null and b=7 or a > 1 and a < 3 limit 1; explain select * from t1 where a > 8 and a < 9; explain select * from t1 where b like "6%"; select * from t1 where a is null; select * from t1 where a is null and b = 7 and c=0; select * from t1 where a<=>b limit 2; select * from t1 where (a is null or a > 0 and a < 3) and b < 5 limit 3; select * from t1 where (a is null or a > 0 and a < 3) and b > 7 limit 3; select * from t1 where (a is null or a = 7) and b=7 and c=0; select * from t1 where a is null and b=9 or a is null and b=7 limit 3; select * from t1 where b like "6%"; drop table t1;