-- 求高手解答如何创建年龄段约束、默认约束、以及外键约束
drop database if exists StudentDB;
create database StudentDB;
use StudentDB;
create table StudentInfo
(
StuName varchar(8) not null,
StuNo char(6) not null,
StuSex char(2) not null,
StuAge tinyint not null,
StuSeat tinyint not null,
StuAddress varchar(50),
constraint PK_StudentInfo_StuSeat primary key (StuNo),
constraint CK_StudentInfo_StuSex check(StuSex in('男','女'))
-- constraint CK_StudentInfo_StuNo check(StuNo like 's253[0-9][0-9]'),
-- constraint CK_StudentInfo_StuAge check(StuAge < 40 and StuAge > 15),
-- constraint CK_StudentInfo_StuSeat check(StuSeat < 30 and StuSeat > 0)
-- constraint DF_StudentInfo_StuAddress default '地址不详'
);
-- 加入测试数据
insert into StudentInfo values('张秋丽','s25301','女',18,1,'北京海淀'),
('李斯文','s25303','男',22,2,'北京海淀'),
('李文才','s25302','男',85,3,'地址不详'),
('欧阳俊雄','s25304','男',28,4,'新疆'),
('梅超风','s25318','女',23,5,'');
use StudentDB;
create table StudentMarks
(
ExamNo char(7) not null,
StuNo char(6) not null,
WrittenE
我以前安装了一次，后来卸载了，现在再安装的时候，提示错误：Error 1305.Error reading from file C:DOCUME~1\LOCALS~1\Temp\mysql_server.msi.Verify that the file exists and that you can access it.
� ......
MYSQL 截取一个数据表中,某一个字段(fulltext) 的前三百个字符,放到该表下另一个字段(introtxt)里.
求实现这个效果的命令
SQL code:
update 表 set introtxt=left(`fulltext`,300);
顶，学习
SQL code: ......
