作为备忘吧.在机房里输入的.
/*CREATE TABLE Student
(Sno CHAR(9) PRIMARY KEY,
Sname CHAR(20) UNIQUE,
Ssex CHAR(2),
Sage SMALLINT,
Sdept CHAR(20)
);*/
/*CREATE TABLE Course
(Cno CHAR(4) PRIMARY KEY,
Cname CHAR(40),
Cpno CHAR(4),
Credit SMALLINT,
FOREIGN KEY (Cpno) REFERENCES Course(Cno)
);*/
/*ALTER TABLE Student ADD S_entrance CHAR;*/
/*ALTER TABLE Student ALTER COLUMN Sage INT;*/
/*ALTER TABLE Course ADD UNIQUE(Cname);*/
/*INSERT
INTO Student (Sno, Sname, Ssex, Sage,Sdept)
VALUES ('200815128', '陈冬', '男', '20', 'IS');*/
/*INSERT
INTO Student (Sno, Sname, Ssex, Sage,Sdept)
VALUES ('200815129', '李芬', '女', '20', 'SR');*/
/*INSERT
INTO Student (Sno, Sname, Ssex, Sage,Sdept)
VALUES ('200815130', '洋洋', '男', '19', 'SR');*/
/*INSERT
INTO Student (Sno, Sname, Ssex, Sage, Sdept)
VALUES ('200815131', '吴建国', '男', '21', 'IS');*/
/*INSERT
INTO Student (Sno, Sname, Ssex, Sage,Sdept)
VALUES ('200815132', '陈浩南', '男', '20', 'SC');*/
/*INSERT
INTO Student (Sno, Sname, Ssex, Sage, Sdept)
VALUES ('200815133', '春冬', '女', '22', 'SC');*/
UPDATE Student
SET S_entrance = '8'
WHERE S_entrance IS NULL;
SELECT *
from Student
SQL语言由命令、子句、运算和集合函数等构成。在SQL中，数据定义语言DDL（用来建立及定义数据表、字段以及索引等数据库结构）包含的命令有CREATE、DROP、ALTER；数据操纵语言DML（用来提供数据的查询、排序以及筛选数据等功能）包含的命令有SELECT、INSERT、UPDATE、DELETE。
一、SQL语句
（1）Select 查询语句
语法：SE ......
