When a primary key constraint is defined, the federated system automatically creates a unique index specification.
当定义一个主键约束时，联邦系统自动创建一个惟一的索引规范。
2
Listings 5 and 6 show sample constraint failures returned from the database system.
清单5和6显示了从数据库系统中返回的失败的约束示例。
3
He identified a shortage of credit as a big obstacle to growth and a shortage of capital in the banking system as the biggest constraint to increasing credit.