【轉】sql 創建表、刪除表 增加字段 刪除字段操作
下面是Sql Server 和 Access 操作數據庫結構的常用Sql，希望對你有所幫助。
新建表：
create table [表名]
(
[自動編號字段] int IDENTITY (1,1) PRIMARY KEY ,
[字段1] nVarChar(50) default \'默認值\' null ,
[字段2] ntext null ,
[字段3] datetime,
[字段4] money null ,
[字段5] int default 0,
[字段6] Decimal (12,4) default 0,
[字段7] image null ,
)
刪除表：
Drop table [表名]
插入數據：
INSERT INTO [表名] (字段1,字段2) VALUES (100,\'51WINDOWS.NET\')
刪除數據：
DELETE FROM [表名] WHERE [字段名]>100
更新數據：
UPDATE [表名] SET [字段1] = 200,[字段2] = \'51WINDOWS.NET\' WHERE [字段三] = \'HAIWA\'
新增字段：
ALTER TABLE [表名] ADD [字段名] NVARCHAR (50) NULL
刪除字段：
ALTER TABLE [表名] DROP COLUMN [字段名]
修改字段：
ALTER TABLE [表名] ALTER COLUMN [字段名] NVARCHAR (50) NULL
重命名表：(Access 重命名表，請參考文章：在Access數據庫中重命名表)
sp_rename \'表名\', \'新表名\', \'OBJECT\'
新建約束：
ALTER TABLE [表名] ADD CONSTRAINT 約束名 CHECK ([約束字段] <= \'2000-1-1\')
刪除約束：
ALTER TABLE [表名] DROP CONSTRAINT 約束名
新建默認值
ALTER TABLE [表名] ADD CONSTRAINT 默認值名 DEFAULT \'51WINDOWS.NET\' FOR [字段名]
刪除默認值
ALTER TABLE [表名] DROP CONSTRAINT 默認值名
刪除Sql Server 中的日志，減小數據庫文件大小
dump transaction 數據庫名 with no_log
backup log 數據庫名 with no_log
dbcc shrinkdatabase(數據庫名)
exec sp_dboption \'數據庫名\', \'autoshrink\', \'true\'
\\\'添加字段通用函數
Sub AddColumn(TableName,ColumnName,ColumnType)
Conn.Execute(\"Alter Table \"&TableName&\" Add \"&ColumnName&\" \"&ColumnType&\"\")
End Sub
\\\'更改字段通用函數
Sub ModColumn(TableName,ColumnName,ColumnType)
Conn.Execute(\"Alter Table \"&TableName&\" Alter Column \"&ColumnName&\" \"&ColumnType&\"\")
End Sub
\\\'檢查表是否存在
sql=\"select count(*) as dida from sysobjects where id = object_id(N\'[所有者].[表名]\') and OBJECTPROPERTY(id, N\'IsUserTable\') = 1\"
set rs=conn.execute(sql)
response.write rs(\"dida\")\'返回一個數值，0代表沒有，1代表存在
判斷表的存在:
select * from sysobjects where id = object_id(N\'[dbo].[tablename]\') and OBJECTPROPERTY(id, N\'IsUserTable\') = 1
某個表的結構
select * from syscolumns where id = object_id(N\'[dbo].[你的表名]\') and OBJECTPROPERTY(id, N\'IsUserTable\') = 1
create table student(
Sno int not null primary key,
Sname char(10)not null,
Ssex bit not null,
Sage tinyint not null,
Sdept char(20) not null)
create table course(
Cno int not null primary key,
Cname char(20)not null,
Cpno int not null,
Ccredit tinyint not null)
create table sc(
Sno int not null,
Cno int not null,
Grade tinyint not null
foreign key(Sno)references student(Sno)
foreign key(Cno)references course(Cno)
)
(1)
seleCt top 1 S.sno,sname
from SC,S
where Cno='C2' and SC.sno=S.sno
order by grade desC;
(2)
seleCt sname,age
from Student,SC
where SC.sno not in(
seleCt SC.sno
from SC
where Cno='C2' )and SC.sno=S.sno;
(3)
seleCt sno, avg(grade) as average
from SC
group by sno
having(avg(grade)>80);
(3)法二
seleCt sno, avg(grade) ' average'
from SC
group by sno
having(avg(grade)>80);
(4)
delete from SC
where SC.sno in(
seleCt sno
from S
where sname='S5');
(5)
seleCt sname
from S
where sdept='英語'and sex='男';
(6)
seleCt SC.sno,avg(grade) as average
from S,SC
where S.sno=SC.sno
group by SC.sno;