更新时间:2023-01-29 16:51:02
如果empName是VARCHAR(50)列:
If empName is a VARCHAR(50) column:
ALTER TABLE Employees MODIFY COLUMN empName VARCHAR(50) AFTER department;
编辑
根据评论,您也可以执行以下操作:
Per the comments, you can also do this:
ALTER TABLE Employees CHANGE COLUMN empName empName VARCHAR(50) AFTER department;
请注意,重复empName
是故意的.您必须告诉MySQL您想保持相同的列名.
Note that the repetition of empName
is deliberate. You have to tell MySQL that you want to keep the same column name.
您应该注意,两种语法版本都特定于MySQL.例如,它们在PostgreSQL或许多其他DBMS中将无法使用.
You should be aware that both syntax versions are specific to MySQL. They won't work, for example, in PostgreSQL or many other DBMSs.
另一个正如@Luis Rossi在评论中指出的那样,您需要在AFTER
修饰符之前完全指定更改后的列定义.上面的示例仅包含VARCHAR(50)
,但是如果您需要其他特征(例如NOT NULL
或默认值),则还需要包括这些特征.有关更多信息,请参考 ALTER TABLE
上的文档.
Another edit: As pointed out by @Luis Rossi in a comment, you need to completely specify the altered column definition just before the AFTER
modifier. The above examples just have VARCHAR(50)
, but if you need other characteristics (such as NOT NULL
or a default value) you need to include those as well. Consult the docs on ALTER TABLE
for more info.