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。

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A general, good practice is not to allow null (that is, no value) columns in a relational database, because when you attempt to read such a column, you get a null value exception.

通常，一种优秀的实践就是不要在关系数据库中使用null(即没有值)列，因为当您试图读取这类列时，您将得到一个null值异常。

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If the stock is not produced, then the shorting transaction will be null and void and the broker will have to purchase the stock, says Jamie Selway, managing director at White Cap Trading.

FORBES: Magazine Article

Translation, if one were to start with a pre-trial null hypothesis probability of 50% (reflecting equipoise, an ethical prerequisite for randomizing patients), the post-trial null hypothesis probability would still be 9%, which is not sufficient to change my practice.

FORBES: Chelation For Heart Disease: Not What You Have Read

As a result, Botha has turned to the courts in an attempt to have his Bulls contract declared null and void, while Sarfu has not confirmed whether his Springbok contract is part of his court application.

BBC: Strike threat to Springbok tour