题目内容
关系是关系模式某一时刻的状态或内容
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实体完整性指的是主属性具有唯一性
参照完整性是对外码的约束
in air cargo transportation, the freight cost must be paid in advance, otherwise the carrier has right to reject the shipment.
The pricing of international air freight is governed by the IATA via the TACT,and the air carriers worldwide are required to use the rates and charges specified in TACT.()2015
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