如果列上有数据偏离，评估结果就可能不正确。

The estimate could be incorrect if there is data skew on the column.

youdao

因为很容易错误地使用字段，所以随着时间的推移，输入的数据值逐渐偏离了数据模型中的定义。

Because it was often easier to misuse a field than to change the application, the data values as entered drifted over time away from the data models.

youdao

换句话说，列上的数据有偏离。

In other word, there is data skew on the column.

youdao