创建模式
 create schema <schema_name> authorization <username> 没有指定schema_name时默认是用户名

 删除模式
 drop schema <schema_name> <cascade | restrict>

 创建表
 create table student.sc            ;定义表中的两个主码以及外码
 (sno ),
 cno ),
 grade smallint,
 primary key(sno, cno),
 foreign key sno references student(sno),
 foreign key sno references course(cno)
 );                    /*最后一行没有逗号，外码引用的必须是主码*/

 修改表
 alter table <table_name>
 [ add <新列名> <数据类型> [完整性约束] ]
 [ drop [完整性约束名] [列名] ]
 [ modify <列名> <数据类型> ];

 删除表

 drop table <表名>;

 创建索引
 create [unique] [cluster] index <索引名>
 on <表名>( <列名> [ <次序> ] [, <列名> [ <次序> ] ] ....);

 删除索引
 drop index <索引名>

 插入元组
 insert
 into <表名> [ ( <属性列1> [, <属性列2>...] ) ]
 values ( <常量1> [, <常量2>] ... )

 insert into sc(sno,cno)
 ')

 修改元组
 update <表名>
 set <列名> = <表达式> [, <列名> = <表达式> ]...
 [where <条件>];

 update student

 '

 删除元组
 delete
 from <表名>
 [where <条件> ];

 delete
 from student
 '

 使用视图创建语句建视图，通过视图查询数据:
 create view <视图名> [(<列名>[,<列名>]...)]            ;列名要么全部指定，要么全部不指定
 as
 <子查询>
 [with check option];

 drop view <视图名>;

 创建用户
 create user <username> [with] [DBA | RESOURCE | CONNECT];
 create user  zx_root   IDENTIFIED by 'xxxxx@localhost';

 删除用户
 drop user <username>;

 授权
 grant <权限> [,<权限> ]...                    ;all privileges, select, update, insert, delete
 on <对象类型> <对象名> [,<对象类型> <对象名>]...
 to <用户> [,<用户>]...                        ;public
 [with grant option];

 grant all privileges
 on table student, course
 to u2, u3;

 grant update(sno)
 on table student
 to u4;

 grant insert
 on table sc
 to u5
 with grant option

 回收授权
 revoke <权限>[,<权限>]...
 on <对象类型> <对象名> [,<对象类型> <对象名>]...
 from <用户> [,<用户>]...

 revoke select
 on table sc
 from public

 创建角色
 create role <rolename>

 给角色授权
 grant <权限> [,<权限>]...
 on <对象类型> <对象名>
 to <角色> [,<角色>]...

 grant <角色1> [,<角色2>]...
 to <角色3> [,<角色4>]...
 [with admin option]

 收回角色权限
 revoke <权限> [,<权限>]...
 on <对象类型> <对象名>
 from <角色> [,<角色>]...

 create role r1;

 grant select, update, insert
 on table student
 to r1;

 grant r1
 to 王平,张明

 revoke select
 on table student
 from r1;

 审计

 audit alert,update
 on sc;

 noaudit all
 on sc;

 实体完整性
 primary key(sno,cno);

 参照完整性
 foreign key sno reference student(sno);

 用户定义完整性
 create table sc
 (sno ) not null,
 cno ) not null,
 grade smallint not null,);

 create table dept
 (deptno number,
 dname ) unique,
 );

 create table student
 (sno ) primary key,
 ssex ) check (ssex in ('男','女')),);

 表级用户定义完整性
 check (ssex = '女' or sname not like 'ms.%' );            /*男性名字不能以ms.开头*/

 完整性约束命名子句
 constraint <完整性约束条件名> [primary key短语 | foreign key 短语 | check 短语]

 create stable student
 (sno )
      ),
 sname )
     constraint c2 not null,
 sage )
     ),
 ssex )
     constraint c4 check (ssex in ('男','女'),
 constraint studentKey primary key(sno),
 );

 alter table student
 drop constraint c4;

 alter table student
 add constraint c4 check (ssex in ('男','女'));

 域中完整性限制
 )
 constraint gd check (value in ('男','女'));

 alter domain genderdomain
 '));

 alter domain genderdomain
 drop constraint gd;

 查询
 seletct [ all | distinct ] <目标列表达式> [, <目标列表达式> ]...
 from <表名或视图名> [, <表名或视图名> ]...
 [ where <条件表达式> ]
 [ group by <列名1> [ having <条件表达式> ] ]
 [ order by <列名2> [ asc | desc ] ]

 表单查询

 -sage year
 from student

 select sname, sdept, sage
 from student
          /*not between and*/

 select sname, ssex
 from student
 where sdept in ('cs','ma','is')     /*not in*/

 select *
 from student
 where sno like '2002%21'            /*%任意多个字符,_单个字符, [ escape '\' ] 表示'\'为换码字符，not like */

 select sno,cno
 from sc
 where grade is null            /*is not*/

 select sno,grade
 from sc
 '
 order by grade desc,sno

 select cno, count( distinct sno )
 from sc
 group by cno

 连接查询，嵌套查询

 select sname
 from student
             /*or, not*/

 select first.cno, second.cpno
 from course first, course second
 where first.cpno = second.cno                /*<>是不等于*/

 select sname
 from student
 where sno in
     (select sno
     from sc
     ' );

 select sno,cno
 from sc x
 where grade >=
     (select avg(grade)
     from sc y
     where y.sno = x.sno);

 select sname,sage
 from student
 where sage < any
     (select sage
     from student
     where sdept = 'cs');            /*all*/

 select sname
 from student
 where not exists
     (select *
     from course
     where not exists
         (select *
         from sc
         where sno = student.sno
         and    cno = course.cno ));            /*not exists 没有*/

 集合查询:

 select *
 from student
 where sdept='cs'
 union
 select *
 from student
 ;

 select *
 from student
 where sdept='cs'
 intersect
 select *
 from student
 ;

 select *
 from student
 where sdept='cs'
 except
 select *
 from student
 ;

 数据类型
 char(n)                长度为n的定长字符串
 varchar(n)                最大长度为n的可变字符串
 int                    长整形,可写作integer
 smallint                短整形
 numberic(p,d)            定点数，有p位数字（不包括符号，小数点）组成，小数点后有d位小数
 real                    取决于机器精度的浮点数
 double precision            取决于机器精度的双精度浮点数
 float(n)                浮点数，精度至少为n为数字
 date                    日期,YYYY-MM-DD
 time                    时间,HH:MM:SS

 小问题

 "=" 两边可以没有空格

 实例：

 create DataBase SpjDB
 on (name=spj_dat,
 filename='D:\Sql_Server\spj_data.mdf',
 size=10mb)
 log
 on (name=spj_log,
 filename='D:\Sql_Server\spj_log.ldf',
 size=3mb)

 Create table S
 (SNO ) primary key,
 SNAME ),
 STATUS smallint,
 CITY ))

 insert into s
 ','天津');

 insert into s
 ','北京');

 Create table p
 (PNO ) primary key,
 PNAME ),
 COLOR ),
 WEIGHT smallint)

 insert into P
 ');
 insert into P
 ');
 insert into P

 Create table J
 (JNO ) primary key,
 PNAME ),
 CITY ))

 insert into J
 values('J1','三建','北京');
 insert into J
 values('J2','一汽','长春');
 insert into J

 Create table SPJ
 (SNO ),
 PNO ),
 JNO ),
 QTY smallint)

 insert into SPJ
 ');
 insert into SPJ
 ');