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create table t1(a blob unique , b blob , c blob, unique(b,c));
insert into t1 values(1,1,1);
insert into t1 values(2,2,2),(3,3,3),(4,4,4),(5,5,5);
insert into t1 select a+5, b+5, c+5 from t1;
insert into t1 select a+10, b+10, c+10 from t1;
insert into t1 select a+20, b+20, c+20 from t1;
insert into t1 select a+40, b+40, c+40 from t1;
explain select * from t1 where a="34";;
id 1
select_type SIMPLE
table t1
type ref
possible_keys a
key a
key_len 9
ref const
rows 8
Extra Using where; Full scan on NULL key
explain select * from t1 where b="34" and c = "34";;
id 1
select_type SIMPLE
table t1
type ref
possible_keys b
key b
key_len 9
ref const
rows 8
Extra Using where; Full scan on NULL key
explain select * from t1 where c="34" and b="34";;
id 1
select_type SIMPLE
table t1
type ref
possible_keys b
key b
key_len 9
ref const
rows 8
Extra Using where; Full scan on NULL key
explain select * from t1 where c="34";;
id 1
select_type SIMPLE
table t1
type ALL
possible_keys NULL
key NULL
key_len NULL
ref NULL
rows 80
Extra Using where
explain select * from t1 where b="34";;
id 1
select_type SIMPLE
table t1
type ALL
possible_keys b
key NULL
key_len NULL
ref NULL
rows 80
Extra Using where
select * from t1 where a="34";
a b c
34 34 34
select * from t1 where b="34" and c = "34";
a b c
34 34 34
select * from t1 where c="34" and b="34";
a b c
34 34 34
select * from t1 where c="34";
a b c
34 34 34
select * from t1 where b="34";
a b c
34 34 34
drop table t1;
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