摘要：/*第二章 作业*/create table S( sno char(2) NOT NULL UNIQUE, sname char(3), city char(2));alter table S add constraint s_k primary key(sno);create table P( pno char(2) NOT NULL, pname char(3), color char(1), weight int);alter table P add constraint p_k primary key(pno);create table J(... 阅读全文