约束支持主键、外键、惟一和非空约束。
Constraints Supports, primary, foreign, unique, not null constraint.
一些约束不会有变化（非空、数据库中的最大长度），但有一些会因国家而不同。
Some constraints will not change (not null, maximum length in the database), but some will vary with the country.
这种校验会通过拒绝空值，强迫加上非空[notNULL]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。
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.
简单的例子比如典型的名称唯一性约束、类型检查或非空检查。
Simple examples include the typical name-uniqueness constraints, type checks or non-nullness.
未能启用约束。一行或多行中包含违反非空、唯一或外键约束的值。
Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
设计域完整性属性。考虑CHECK约束，数据类型和是否非空。
Design attribute domain integrity. Considerations include CHECK constraints, data types, and nullability.
设计域完整性属性。考虑CHECK约束，数据类型和是否非空。
Design attribute domain integrity. Considerations include CHECK constraints, data types, and nullability.
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