DEFAULT 默认值

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最新推荐文章于 2024-03-12 19:46:29 发布

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每当插入一个记录时候 假设没有明确字段赋值 则自动赋予默认值；

mysql> CREATE TABLE eight(
    -> id SMALLINT UNSIGNED  AUTO_INCREMENT PRIMARY KEY,
    -> username VARCHAR(20) NOT NULL UNIQUE KEY,
    -> sex ENUM ("1","2","3") DEFAULT'3'                     DEFAULT设置默认值;
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> SHOW COLUMNS FROM eight;
+----------+----------------------+------+-----+---------+----------------+
| Field    | Type                 | Null | Key | Default | Extra          |
+----------+----------------------+------+-----+---------+----------------+
| id       | smallint(5) unsigned | NO   | PRI | NULL    | auto_increment |
| username | varchar(20)          | NO   | UNI | NULL    |                |
| sex      | enum('1','2','3')    | YES  |     | 3       |                |
+----------+----------------------+------+-----+---------+----------------+
3 rows in set (0.03 sec)

mysql> INSERT EIGHT (USERNAME)VALUES('feiyu');
Query OK, 1 row affected (0.00 sec)

mysql> SELECT * FROM eight;
+----+----------+------+
| id | username | sex  |
+----+----------+------+
|  1 | feiyu    | 3    |
+----+----------+------+
1 row in set (0.00 sec)

mysql>