仅显示MySQL中为列设置的默认值
让我们首先创建一个表并设置默认值-
mysql> create table DemoTable803(UserId int DEFAULT 101,UserName varchar(100) DEFAULT 'Chris');
使用insert命令在表中插入一些记录。对于我们不插入的值，默认值将自动设置-
mysql> insert into DemoTable803 values(102,'Chris');
mysql> insert into DemoTable803(UserName) values('Mike');
mysql> insert into DemoTable803(UserId) values(103);
mysql> insert into DemoTable803 values();
mysql> insert into DemoTable803 values(110,'Robert');使用select语句显示表中的所有记录-
mysql> select *from DemoTable803;
这将产生以下输出-
+--------+----------+ | UserId | UserName | +--------+----------+ | 102 | Chris | | 101 | Mike | | 103 | Chris | | 101 | Chris | | 110 | Robert | +--------+----------+ 5 rows in set (0.00 sec)
以下是仅显示默认值的查询-
mysql> select default(UserId),default(UserName) from DemoTable803 limit 1;
这将产生以下输出-
+-----------------+-------------------+ | default(UserId) | default(UserName) | +-----------------+-------------------+ | 101 | Chris | +-----------------+-------------------+ 1 row in set (0.00 sec)