The ________ provide(s) information on each attribute and why the attribute is needed in the database, who uses it, and how it should be updated.
A. business rules
B. cardinality
C. data dictionary
D. modality
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A vertical line with a “chicken leg” to the entity represents the ________ cardinality symbol.
A. mandatory many
B. mandatory single
C. optional many
D. optional single
A circle with a “chicken leg” to the entity represents the ________ cardinality symbol.
A. mandatory many
B. mandatory single
C. optional many
D. optional single
Considering the following tables, ________ is a primary key.
A. Class Table: PID
B. Professor Table: Name
C. Student Table: Expected Graduation Year
D. Student Table: ID
《进口许可证》原则实行“一批一证”制度,非“一批一证”的商品发证机关在签发进口许可证时必须在“备案”栏注明“非一批一证”字样,该证在有效期内最多可使用:( )。
A. 12次
B. 8次
C. 6次
D. 4次