数据库算法.doc

示例：course(cno, cname, cpno, ccredit) cno列是主码，cname列不允许有重复值 create table course ( cno char(1) constraint PK_course_cno primary key, cname varchar(20) constraint UQ_course_cname unique, cpno char(1), ccredit smallint ); create table course ( cno char(1), cname varchar(20), cpno char(1), ccredit smallint, constraint PK_course_cno primary key(cno), constraint UQ_course_cname unique(cname) ); 示例：course(cno, cname, cpno, ccredit) cno列是主码，cname列不允许有重复值，ccredit大于零 create table course ( cno char(1) constraint PK_course_cno primary key, cname varchar(20) constraint UQ_course_cname unique, cpno char(1), ccredit smallint constraint CK_course_ccredit check(ccredit0) ); create table course ( cno char(1) constraint PK_course_cno primary key, cname varchar(20) constraint UQ_course_cno unique, cpno char(1), ccredit smallint, constraint CK_course_ccredit check(ccredit0) ); 示例：course(cno, cname, cpno, ccredit)cno列是主码，cname列不允许有重复值，ccredit大于0小于等于4 create table course ( cno char(1) constraint PK_course_cno primary key, cname varchar(20) constraint UQ_course_cname unique, cpno char(1), ccredit smallint, constraint CK_course_ccredit check(ccredit0 and ccredit=4) ); 示例： student( sno, sname, ssex, sage, sdept )sno列为主码，sname列不能取空值， sage默认值为20 create table student ( sno char( 5 ), sname varchar( 20 ) not null, ssex char( 2 ), sage smallint constraint DF_student_sage default(20), sdept varchar(15), constraint PK_student_sno primary key( sno ) ); 示例： sc(sno, cno, grade) (sno, cno)列为主码， sno列为外码，cno列为外码 create table sc ( sno char(5) constraint FK_sc_sno foreign key references student(sno), cno char(1) constraint FK_sc_cno foreign key references course(cno), grade int, constraint PK_sc_snocno primary key(sno, cno) ); 示例： sc(sno, cno, grade) (sno, cno)列为主码， sno列为外码，cno列为外码