使用循环在SPSS中创建指标变量(Create indicator variables in SPSS using loops)

 您不需要ALTER语句，但可以在获取类似数据时将其转换为datetime时间 
 
select cast(order_date as datetime) as new_date
from table1;
 
 但是你不应该把日期时间数据存储为字符串或varchar 。 它应该只存储在datetime数据类型列中。 现在，由于您已经有该列中的数据， ALTER看起来有点误导。 
 
 您可以备份当前的数据。 创建一个具有order_date datetime相同结构的中间表。 然后执行一个insert into .. select from下面的insert into .. select from 。 然后可能将该表重命名为原始表（在此之前删除现有表）; 
 
insert into intermediary_table
select col1,col2, cast(order_date as datetime), col3
from table1;

You don't need a ALTER statement but can convert that to datetime while fetching the data like
 
select cast(order_date as datetime) as new_date
from table1;
 
But you should never store datetime data as string or varchar. It should be stored in datetime datatype column only. Now, since you already have data in that column; ALTER looks bit misleading.
 
You can take a backup of your current data. Create a intermediary table with same structure having order_date datetime. Then perform a insert into .. select from like below. Then probably rename that table to original table (before that drop the existing table);
 
insert into intermediary_table
select col1,col2, cast(order_date as datetime), col3
from table1;