null value

常见例句

Unless you have a very specific reason to use a NULL value, you should always set your columns as NOT NULL.
除非你有一个很特别的原因去使用 NULL 值，你应该总是让你的字段保持 NOT NULL。这看起来好像有点争议，请往下看。
yq329.blog.163.com
This new validation will enforce NOT NULL column constraints by rejecting null values, but only in situations where your database would reject a null value.
这种校验会通过拒绝空值，强迫加上非空[NOT NULL]字段的约束，但是也只有在这种情况下，你的数据库会拒绝空值。
As you saw in Section 1, DB2 implicitly allocates memory for arrays when they are initialized with a non-NULL value or when they grow past their current size.
正如您在第 1 部分中所看到的，在通过非 NULL 值初始化阵列时或阵列增长超过它们当前大小时，DB2 会隐式为阵列分配内存。