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create table t1(a blob , unique(a) using hash);
show keys from t1;;
Table t1
Non_unique 0
Key_name a
Seq_in_index 1
Column_name a
Collation A
Cardinality NULL
Sub_part NULL
Packed NULL
Null YES
Index_type HASH
Comment
Index_comment
drop table t1;
create table t1(a blob , unique(a) using btree);
ERROR 42000: Specified key was too long; max key length is 1000 bytes
create table t1(a int , unique(a) using hash);
show keys from t1;;
Table t1
Non_unique 0
Key_name a
Seq_in_index 1
Column_name a
Collation A
Cardinality NULL
Sub_part NULL
Packed NULL
Null YES
Index_type HASH
Comment
Index_comment
drop table t1;
create table t1(a int ,b int , c int, unique(a, b, c) using hash);
show keys from t1;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
t1 0 a 1 a A NULL NULL NULL YES HASH
t1 0 a 2 b A NULL NULL NULL YES HASH
t1 0 a 3 c A NULL NULL NULL YES HASH
insert into t1 values(1,1,1);
insert into t1 values(1,1,1);
ERROR 23000: Duplicate entry '1-1-1' for key 'a'
drop table t1;
create table t1(a int ,b int , c int, unique(a, b, c) using hash) engine=memory;
show keys from t1;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
t1 0 a 1 a NULL NULL NULL NULL YES HASH
t1 0 a 2 b NULL NULL NULL NULL YES HASH
t1 0 a 3 c NULL 0 NULL NULL YES HASH
insert into t1 values(1,1,1);
insert into t1 values(1,1,1);
ERROR 23000: Duplicate entry '1-1-1' for key 'a'
drop table t1;
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