ALTER TABLE [Employee]
ALTER COLUMN [Salary] NUMERIC(22,5) NOT NULL

有趣的方法可以在这里找到:如何扩大你的专栏没有停机由spaghettidba

If you try to enlarge this column with a straight “ALTER TABLE” command, you will have to wait for SQLServer to go through all the rows and write the new data type ALTER TABLE tab_name ALTER COLUMN col_name new_larger_data_type; To overcome this inconvenience, there is a magic column enlargement pill that your table can take, and it’s called Row Compression. (...) With Row Compression, your fixed size columns can use only the space needed by the smallest data type where the actual data fits.

当表在ROW级别被压缩时，ALTER table ALTER COLUMN是仅元数据的操作。

ALTER TABLE [Employee]
ALTER COLUMN [Salary] NUMERIC(22,5) NOT NULL

alter table Employee alter column salary numeric(22,5)

右键单击需要修改的表格——>选择“Design”——>修改“Data Type”列的值，如下图所示:

然后保存以完成对表设计的更改。

小表采用GUI方法。 你在大的表中做改变，然后只使用命令，并排检查阻塞是否发生，直到命令完成。

对于Oracle数据库:

VARCHAR2(255 CHAR);