学习ALTER TABLE删除、添加和修改字段和类型
CREATE TABLE alter_tab01(
id int,
col01 char(20))
engin=InnoDB default charset=utf8;
删除字段
ALTER TABLE DROP ;
mysql> alter table alter_tab01 dropcol01;
Query OK, 0 rows affected (0.01sec)
Records: 0 Duplicates: 0 Warnings: 0
添加字段
ALTER TABLE ADD TYPE;
ALTER TABLE ADD TYPE [ FIRST| AFTER ];
ALTER TABLE ADD TYPE NOT NULL;
mysql> alter table alter_tab01 add col01 char(20);
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table alter_tab01 add col02 char(20) first;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table alter_tab01 add col03 char(20) after id;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table alter_tab01 add col04 char(20) not null;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> show columns from alter_tab01;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| col02 | char(20) | YES | | NULL | |
| id | int(11) | YES | | NULL | |
| col03 | char(20) | YES | | NULL | |
| col01 | char(20) | YES | | NULL | |
| col04 | char(20) | NO | | NULL | |
+-------+----------+------+-----+---------+-------+
5 rows in set (0.00 sec)
修改字段类型及名称
ALTER TABLE MODIFY TYPE;
ALTER TABLE CHANGE TYPE;
mysql> alter table alter_tab01 modify col02 varchar(10);
Query OK, 0 rows affected (0.01sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> alter table alter_tab01 change col02 new_col02 char(2);
Query OK, 0 rows affected (0.01sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> show columns fromalter_tab01;
+-----------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+----------+------+-----+---------+-------+
| new_col02 | char(2) | YES | | NULL | |
| id | int(11) | YES | | NULL | |
| col03 | char(20) | YES | | NULL | |
| col01 | char(20) | YES | | NULL | |
| col04 | char(20) | NO | | NULL | |
+-----------+----------+------+-----+---------+-------+
5 rows in set (0.00 sec)
修改字段NOT NULL约束与默认值
ALTER TABLE MODIFY TYPE NOT NULL DEFAULT ;
mysql> alter table alter_tab01 modify id bigint not null default 1;
Query OK, 0 rows affected (0.01sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> show columns fromalter_tab01;
+-----------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+------------+------+-----+---------+-------+
| new_col02 | char(2) | YES | | NULL | |
| id | bigint(20) | NO | | 1 | |
| col03 | char(20) | YES | | NULL | |
| col01 | char(20) | YES | | NULL | |
| col04 | char(20) | NO | | NULL | |
+-----------+------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
修改字段的默认值
ALTER TABLE ALTER SET DEFAULT ;
ALTER TABLE ALTER DROP DEFAULT;
mysql> alter table alter_tab01 alter new_col02 set default '01';
Query OK, 0 rows affected (0.01sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> show columns fromalter_tab01;
+-----------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+------------+------+-----+---------+-------+
| new_col02 | char(2) | YES | | 01 | |
| id | bigint(20) | NO | | 1 | |
| col03 | char(20) | YES | | NULL | |
| col01 | char(20) | YES | | NULL | |
| col04 | char(20) | NO | | NULL | |
+-----------+------------+------+-----+---------+-------+
5 rows in set (0.00sec)
mysql> alter table alter_tab01 alter new_col02 drop default;
Query OK, 0 rows affected (0.00sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> show columns fromalter_tab01;
+-----------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+------------+------+-----+---------+-------+
| new_col02 | char(2) | YES | | NULL | |
| id | bigint(20) | NO | | 1 | |
| col03 | char(20) | YES | | NULL | |
| col01 | char(20) | YES | | NULL | |
| col04 | char(20) | NO | | NULL | |
+-----------+------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
修改表的存储引擎
ALTER TABLE ENGINE=【MyISAM | InnoDB | BDB | Memory | Merge | Archive | Federated | Cluster/NDB | Other】
mysql> show table status like 'alter_tab01'\G
*************************** 1. row ***************************Name: alter_tab01
Engine: InnoDB
Version: 10Row_format: Compact
Rows: 0Avg_row_length: 0Data_length: 16384Max_data_length: 0Index_length: 0Data_free: 4194304Auto_increment: NULLCreate_time: 2018-05-03 16:11:39Update_time: NULLCheck_time: NULLCollation: utf8_general_ci
Checksum: NULLCreate_options:
Comment:
1 row in set (0.00sec)
mysql> alter table alter_tab01 engine=MyISAM;
Query OK, 0 rows affected (0.01sec)
Records: 0 Duplicates: 0 Warnings: 0mysql> show table status like 'alter_tab01'\G
*************************** 1. row ***************************Name: alter_tab01
Engine: MyISAM
Version: 10Row_format: Fixed
Rows: 0Avg_row_length: 0Data_length: 0Max_data_length: 54887620458577919Index_length: 1024Data_free: 0Auto_increment: NULLCreate_time: 2018-05-03 16:12:35Update_time: 2018-05-03 16:12:35Check_time: NULLCollation: utf8_general_ci
Checksum: NULLCreate_options:
Comment:
1 row in set (0.00 sec)
修改表的名称
ALTER TABLE RENAME TO ;
mysql> alter table alter_tab01 rename toalter_tab02;
Query OK, 0 rows affected (0.00sec)
mysql> show table status like 'alter_tab02'\G
*************************** 1. row ***************************Name: alter_tab02
Engine: InnoDB
Version: 10Row_format: Compact
Rows: 0Avg_row_length: 0Data_length: 16384Max_data_length: 0Index_length: 0Data_free: 4194304Auto_increment: NULLCreate_time: 2018-05-03 16:14:02Update_time: NULLCheck_time: NULLCollation: utf8_general_ci
Checksum: NULLCreate_options:
Comment:
1 row in set (0.00 sec)
详解)
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