For sa & d projects , all foreign keys are identified and marked in the entity description part iii ( entity key description ) . for sa & d projects , all entities are in third normal form ( 3nf ) 对于系统分析及设计的计划,所有外键码须经认定,并且在数据实体描述的第iii部分(数据实体关键码描述)界定。
百科解释
In computer science, the third normal form (3NF) is a normal form used in database normalization. 3NF was originally defined by E.