This column should be NOT NULL, and will have no business meaning.

这个列应该是NOT NULL，并且没有商业意义。

youdao

For example, if a before trigger supplies value to a NOT NULL column, then the before trigger is executed first and a value is supplied to the column so that the NOT NULL constraint isn't violated.

例如，如果一个BEFORE触发器给一个NOT null列提供值，那么先执行BEFORE触发器，给列提供值，所以不会违反NOT NULL约束。

youdao

When a unique index is created on a column in Oracle 10g, it ensures that the NOT NULL values entered in that column are unique.

当在Oracle 10 g中的列上创建UNIQUE索引时，会确保此列中输入的NOT null值是惟一的。

youdao