在VARCHAR修改上强制截断？ [英] Force Truncation on VARCHAR modification?

问题描述

我想在几列上将VARCHAR限制为255，以便添加索引。

I would like to cap VARCHAR to 255 on a few columns so that I can add an index.

alter table striker modify contacts varchar(255)

当我尝试运行上述命令时，我得到

When I try to run the above command I get

Error Code: 1265. Data truncated for column 'contacts' at row 331   38.969 sec

是否有一种方法可以强制截断列，以便此命令成功缩短VARCHAR？我不在乎缩短列中的数据。

Is there a way to force truncation of the column so that this command successfully shortens the VARCHAR? I don't care about shortening the data in the column.

推荐答案

您可以手动将列截断为255个字符：

You can manually truncate the column at 255 characters:

UPDATE striker
SET    contacts = SUBSTR (contacts, 1, 255);

现在，您知道没有值超过255个字符，则执行您在OP中安全地拥有的更改表语句。

Now, that you know that no value is longer than 255 characters, you perform the alter table statement you have in the OP safely.

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