1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
|
drop table if exists tt;
create table tt (a int, b int, c int, primary key(a));
insert into tt values (1,0,0),(2,0,0),(3,0,1),(4,0,1);
show indexes from tt;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
tt 0 PRIMARY 1 a A 4 NULL NULL BTREE
analyze table tt;
Table Op Msg_type Msg_text
test.tt analyze status OK
show indexes from tt;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
tt 0 PRIMARY 1 a A 4 NULL NULL BTREE
alter table tt add key (b);
show indexes from tt;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
tt 0 PRIMARY 1 a A 4 NULL NULL BTREE
tt 1 b 1 b A NULL NULL NULL YES BTREE
analyze table tt;
Table Op Msg_type Msg_text
test.tt analyze status OK
show indexes from tt;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
tt 0 PRIMARY 1 a A 4 NULL NULL BTREE
tt 1 b 1 b A 1 NULL NULL YES BTREE
alter table tt add key (c);
show indexes from tt;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
tt 0 PRIMARY 1 a A 4 NULL NULL BTREE
tt 1 b 1 b A NULL NULL NULL YES BTREE
tt 1 c 1 c A NULL NULL NULL YES BTREE
analyze table tt;
Table Op Msg_type Msg_text
test.tt analyze status OK
show indexes from tt;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
tt 0 PRIMARY 1 a A 4 NULL NULL BTREE
tt 1 b 1 b A 1 NULL NULL YES BTREE
tt 1 c 1 c A 2 NULL NULL YES BTREE
flush tables;
show indexes from tt;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
tt 0 PRIMARY 1 a A 4 NULL NULL BTREE
tt 1 b 1 b A 1 NULL NULL YES BTREE
tt 1 c 1 c A 2 NULL NULL YES BTREE
drop table tt;
|