Saturday, September 17, 2022
Saturday, September 17, 2022
Friday, September 16, 2022
Sunday, September 11, 2022
Friday, September 16, 2022
关键字段的描述正确的是()。A、关键字段可以取空值B、关键字段可以重复C、关键字段既可以取空值又可以重复D、关键字段既不能取空值又不能重复...
Sunday, August 13, 2023
Friday, September 16, 2022
Saturday, September 17, 2022
实体完整性规则限制了()的取值。A、全码B、非主属性C、外码D、主属性...
Saturday, July 29, 2023
Saturday, September 17, 2022
对上一级的一个记录不仅有若干个下一级记录相对应,而且对一个下一级记录也有若干个上一级记录相对应的数据是()。A、层次B、网状C、关系D、多对多...
Wednesday, January 3, 2024
子查询的条件不依赖于父查询,这类查询称为嵌套子查询,否则称为()...
Saturday, September 17, 2022
Sunday, September 11, 2022
Sunday, September 11, 2022
Saturday, September 17, 2022
Thursday, August 24, 2023
Friday, September 16, 2022
Saturday, September 17, 2022
FAT32文件系统中DBR的备份位于其DBR扇区之后()个扇区,...
Friday, September 16, 2022
试述关系模型的完整性规则。在参照完整性中,为什么外部码属性的值也...
Sunday, September 11, 2022