MySQL Tutorial/Table/Alter Column - История изменений

в 13:44, 26 мая 2010

2010-05-26T13:44:56Z

Admin: 1 версия

2010-05-26T09:49:14Z

1 версия

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== Add unique constraint to a table using the alter table command==



<source lang="sql">
mysql>
mysql> CREATE TABLE myTable
-> (
-> OrderID SMALLINT UNSIGNED NOT NULL PRIMARY KEY,
-> ModelID SMALLINT UNSIGNED NOT NULL
-> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> desc myTable;
+---------+----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+----------------------+------+-----+---------+-------+
| OrderID | smallint(5) unsigned | NO | PRI | | |
| ModelID | smallint(5) unsigned | NO | | | |
+---------+----------------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql>
mysql> ALTER TABLE myTable
-> ADD UNIQUE (OrderID, ModelID);
Query OK, 0 rows affected (0.06 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql>
mysql> drop table myTable;
Query OK, 0 rows affected (0.00 sec)
mysql></source>

== Changing a Column Name==



<source lang="sql">
mysql>
mysql> CREATE TABLE Employee(
-> id int,
-> first_name VARCHAR(15),
-> last_name VARCHAR(15),
-> start_date DATE,
-> end_date DATE,
-> salary FLOAT(8,2),
-> city VARCHAR(10),
-> description VARCHAR(15)
-> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql>
mysql> ALTER TABLE employee
-> CHANGE First_Name FirstName VARCHAR(20);
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql>
mysql> DESCRIBE employee;
+-------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| FirstName | varchar(20) | YES | | NULL | |
| last_name | varchar(15) | YES | | NULL | |
| start_date | date | YES | | NULL | |
| end_date | date | YES | | NULL | |
| salary | float(8,2) | YES | | NULL | |
| city | varchar(10) | YES | | NULL | |
| description | varchar(15) | YES | | NULL | |
+-------------+-------------+------+-----+---------+-------+
8 rows in set (0.01 sec)
mysql>
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql></source>

== Changing a Column Type==



<source lang="sql">
mysql>
mysql>
mysql> CREATE TABLE Employee(
-> id int,
-> first_name VARCHAR(15),
-> last_name CHAR(15),
-> start_date DATE,
-> end_date DATE,
-> salary FLOAT(8,2),
-> city VARCHAR(10),
-> description VARCHAR(15)
-> );
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql> DESCRIBE employee;
+-------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| first_name | varchar(15) | YES | | NULL | |
| last_name | char(15) | YES | | NULL | |
| start_date | date | YES | | NULL | |
| end_date | date | YES | | NULL | |
| salary | float(8,2) | YES | | NULL | |
| city | varchar(10) | YES | | NULL | |
| description | varchar(15) | YES | | NULL | |
+-------------+-------------+------+-----+---------+-------+
8 rows in set (0.00 sec)
mysql>
mysql>
mysql> ALTER TABLE employee
-> CHANGE Last_Name Last_Name VARCHAR(50);
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql>
mysql> DESCRIBE employee;
+-------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| first_name | varchar(15) | YES | | NULL | |
| Last_Name | varchar(50) | YES | | NULL | |
| start_date | date | YES | | NULL | |
| end_date | date | YES | | NULL | |
| salary | float(8,2) | YES | | NULL | |
| city | varchar(10) | YES | | NULL | |
| description | varchar(15) | YES | | NULL | |
+-------------+-------------+------+-----+---------+-------+
8 rows in set (0.02 sec)
mysql>
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
mysql></source>