Description:
mysql> create table temp (id int not null auto_increment,rem int not null primar
y key,rem2 int not null,unique index1 (id));
Query OK, 0 rows affected (0.03 sec)
mysql> show fields from temp;
+-------+---------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+----------------+
| id | int(11) | | UNI | NULL | auto_increment |
| rem | int(11) | | PRI | 0 | |
| rem2 | int(11) | | | 0 | |
+-------+---------+------+-----+---------+----------------+
3 rows in set (0.02 sec)
mysql> show index from temp;
+-------+------------+----------+--------------+-------------+-----------+------
-------+----------+--------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardi
nality | Sub_part | Packed | Comment |
+-------+------------+----------+--------------+-------------+-----------+------
-------+----------+--------+---------+
| temp | 0 | PRIMARY | 1 | rem | A |
0 | NULL | NULL | |
| temp | 0 | index1 | 1 | id | A |
0 | NULL | NULL | |
+-------+------------+----------+--------------+-------------+-----------+------
-------+----------+--------+---------+
2 rows in set (0.00 sec)
mysql> alter table temp drop primary key;
Query OK, 0 rows affected (0.03 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> show fields from temp;
+-------+---------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+----------------+
| id | int(11) | | PRI | NULL | auto_increment |
| rem | int(11) | | | 0 | |
| rem2 | int(11) | | | 0 | |
+-------+---------+------+-----+---------+----------------+
3 rows in set (0.01 sec)
mysql> show index from temp;
+-------+------------+----------+--------------+-------------+-----------+------
-------+----------+--------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardi
nality | Sub_part | Packed | Comment |
+-------+------------+----------+--------------+-------------+-----------+------
-------+----------+--------+---------+
| temp | 0 | index1 | 1 | id | A |
0 | NULL | NULL | |
+-------+------------+----------+--------------+-------------+-----------+------
-------+----------+--------+---------+
1 row in set (0.00 sec)
How to repeat:
field id is unique key & field rem is primary key , run sql :
alter table temp drop primary key;
the field id change to PRI whit 'show fields from temp' , why not UNI ?
| id | int(11) | | PRI | NULL | auto_increment |
I can't create new primary key .
sorry , my english too bad.
Description: mysql> create table temp (id int not null auto_increment,rem int not null primar y key,rem2 int not null,unique index1 (id)); Query OK, 0 rows affected (0.03 sec) mysql> show fields from temp; +-------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+----------------+ | id | int(11) | | UNI | NULL | auto_increment | | rem | int(11) | | PRI | 0 | | | rem2 | int(11) | | | 0 | | +-------+---------+------+-----+---------+----------------+ 3 rows in set (0.02 sec) mysql> show index from temp; +-------+------------+----------+--------------+-------------+-----------+------ -------+----------+--------+---------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardi nality | Sub_part | Packed | Comment | +-------+------------+----------+--------------+-------------+-----------+------ -------+----------+--------+---------+ | temp | 0 | PRIMARY | 1 | rem | A | 0 | NULL | NULL | | | temp | 0 | index1 | 1 | id | A | 0 | NULL | NULL | | +-------+------------+----------+--------------+-------------+-----------+------ -------+----------+--------+---------+ 2 rows in set (0.00 sec) mysql> alter table temp drop primary key; Query OK, 0 rows affected (0.03 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> show fields from temp; +-------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+----------------+ | id | int(11) | | PRI | NULL | auto_increment | | rem | int(11) | | | 0 | | | rem2 | int(11) | | | 0 | | +-------+---------+------+-----+---------+----------------+ 3 rows in set (0.01 sec) mysql> show index from temp; +-------+------------+----------+--------------+-------------+-----------+------ -------+----------+--------+---------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardi nality | Sub_part | Packed | Comment | +-------+------------+----------+--------------+-------------+-----------+------ -------+----------+--------+---------+ | temp | 0 | index1 | 1 | id | A | 0 | NULL | NULL | | +-------+------------+----------+--------------+-------------+-----------+------ -------+----------+--------+---------+ 1 row in set (0.00 sec) How to repeat: field id is unique key & field rem is primary key , run sql : alter table temp drop primary key; the field id change to PRI whit 'show fields from temp' , why not UNI ? | id | int(11) | | PRI | NULL | auto_increment | I can't create new primary key . sorry , my english too bad.