某医院住院部设有病人关系R（住院号，姓名，性别，、科室号，病房，家庭住址），其中：“住院号”唯一标识关系R中的每一个元组。“性别”的取值只能为M或F；科室关系D（科室号，科室名，负责人，联系电话），其中：“科室号”唯—标识关系D中的每一个元组。创建R关系的SQL语句如下：CREATE TABLER（住院号CHAR（4）PRIMARY KEY,姓名CHAR（10），性别CHAR（1）__（ ）__科室号CHAR（4）__（请作答此空）__家庭住址CHAR（30））；
- A.NOT NULL
- B.REFERENCES D（科室号）
- C.NOT NULL UNIQUE
- D.REFERENCES D（科室名）
正确答案及解析
正确答案
解析
创建表的基本语法：CREATE TABLE＜表名>（＜列名1>＜数据类型>[列级完整性约束条件][,···n]）定义主键使用：PRIMARY KEY或PRIMARY KEY（列名）方式定义外键使用：REFERENCES表名（列）或FOREIGN KEY（列名）REFERENCES表名（列）方式定义自定义约束使用：CHECK（约束表达式）本题第1问是要对性别进行约束，所以需要使用check，由于性别为字符类型需要使用单引号。所以正确的选项应该为：D本题第2问，科室号关联到科室关系，在R关系中科室号应定义为外键，外键定义时应该关联到的是科室关系的科室号，所以正确的选项应为B
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