When ON delete set NULL is active, when a record is deleted from the parent table, all records in the child table with matching foreign key values are set to NULL.

当ON DELETE SET NULL规则被激活时，如果一条记录从父表中删除，子表中的所有记录以及匹配的外键值都被设置为NULL。

youdao

The combined record is much easier to use-you only have to check the PICTURE field to see if it's not null (which was the result of the LEFT OUTER JOIN).

而组合的记录使用起来要容易得多—只需检查PICTURE字段，查看它是否为空(这是LEFT OUTER JOIN的结果)。

youdao

The SIF record format also contains delta specific columns to assist in setting the indicator values of existing database records to NULL.

SIF记录格式还包含特定于delta的列，以协助将现有数据库记录的指示符值设置为NULL。

youdao

Released through Mr. Reznor's own Null Corporation record label, the soundtrack is already available as a download, and will be later released as both a three-CD and six-LP record set.

WSJ: Trent Reznor and Atticus Ross's 'Dragon Tattoo' Score