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SQL经典语句和要点整理

Posted on 2008-01-08 10:43 蓝天旭日 阅读(...) 评论(...) 编辑 收藏
 

                         

*SQL中的保留关键字

action add aggregate all alter after and as asc avg avg_row_length auto_increment between bigint bit binary blob bool both by cascade case char character
change check checksum column columns comment constraint create cross current_date current_time current_timestamp data database databases date datetime day day_hour day_minute
day_second dayofmonth dayofweek dayofyear dec decimal default delayed delay_key_write delete desc describe distinct distinctrow double drop

*得出SQL语句的执行时间的方法

例如:

declare @d datetime

set @d=getdate() select * from ycdata1 select [alltime]=datediff(ms,@d,getdate())

红色为我们要执行的sql语句,结果为 执行花费时间

*清空数据库中所有表的数据(已经测试过,可以正常运行)

declare crsr cursor
 for SELECT [name] FROM DBO.SYSOBJECTS
  WHERE OBJECTPROPERTY(ID,N'IsTable')=1 and type = 'U' and [name] <> 'dtproperties' --and crdate...

open crsr
 declare @tblName sysname
 fetch crsr into @tblName
  EXEC('truncate table '+@tblName)

 while @@fetch_status=0 
 fetch next from crsr into @tblName
  EXEC('truncate table '+@tblName)
close crsr
deallocate crsr  //--
删除以释放游标//可以为crdate字段指定表的创建日期

 

*常用SQL语句扩展和例子

一 数据库筛选记录:

SQL= select * from  tb1 where field1 =’value1’ order by id desc 

Select * from tb1 where field1 like ‘% value1%’ order by id desc

Select top 10 * from tb1 where field1 =’ value1’ order by id,age desc

Select * from tb1 where field1 in(‘value1’, ‘value2’, ‘value3’,)

Select * from tb1 where field1 between value1 and value2

select * from tb1, tb2 where tb1.id *= tb2.id

select a,b,c from tb1 where a IN (select d from b ) //子查询

select * from tb1 where id not in(select id from tb1 where 表达式) order by id desc



更多:

   说明:两张关联表,删除主表中已经在副表中没有的信息

delete from table1 where not exists ( select * from table2 where table1.field1=table2.field1 )

 

说明:Distinct查询数据库存表内不重复的记录

 Select Distinct field1 From tb1

说明:count函数,查询数库表内有多少条记录,“field1”是指同一字段       

  "Select Count(*) From tb1 where field1>#18:0:0# and field1< #19:00# "

说明:两张关联表,删除主表中已经在副表中没有的信息
delete from table1 where not exists ( select * from table2 where table1.field1=table2.field1 )

说明:复制表(只复制结构,源表名:a 新表名:b) (Access可用)
法一:select * into b from a where 1<>1
法二:select top 0 * into b from a

说明:拷贝表(拷贝数据,源表名:a 目标表名:b) (Access可用)
insert into b(a, b, c) select d,e,f from b;

说明:跨数据库之间表的拷贝(具体数据使用绝对路径) (Access可用)
insert into b(a, b, c) select d,e,f from b in ‘具体数据库’ where 条件
例子:..from b in '"&Server.MapPath(".")&""data.mdb" &"' where..

说明:外连接查询(表名1:a 表名2:b)
select a.a, a.b, a.c, b.c, b.d, b.f from a LEFT OUT JOIN b ON a.a = b.c

说明:日程安排提前五分钟提醒
SQL: select * from 日程安排 where datediff('minute',f开始时间,getdate())>5

说明:选择在每一组b值相同的数据中对应的a最大的记录的所有信息(类似这样的用法可以用于论坛每月排行榜,每月热销产品分析,按科目成绩排名,等等.)
select a,b,c from tablename ta where a=(select max(a) from tablename tb where tb.b=ta.b)

说明:包括所有在 TableA 中但不在 TableB和TableC 中的行并消除所有重复行而派生出一个结果表
(select a from tableA ) except (select a from tableB) except (select a from tableC)

说明:列出数据库里所有的表名
select name from sysobjects where type='U'

说明:选择从10到15的记录
select top 5 * from (select top 15 * from table order by id asc) table_别名 order by id desc

说明:一条sql 语句搞定数据库分页
select top 10 b.* from (select top 20 主键字段,排序字段 from 表名 order by 排序字段 desc) a,表名 b where b.主键字段 = a.主键字段 order by a.排序字段

二 数据库更新记录

   sql= update tb1set field1=字段值 where 条件表达式

update tb1 set field1= value1, field2= value2……fieldn= valuen where条件表达式

三 删除记录

   sql= deletefrom tb1 where 条件表达式
deletefrom tb1" //(将数据表所有记录删除)

四 添加记录

  sql=insertinto数据表(field1, field1, field2…)values(value1, value2, value3…)"
insertinto目标数据表select*from源数据表"(把源数据表的记录添加到目标数据表)

五 统计等

    AVG(字段名)得出一个表格栏平均值
COUNT(*|字段名)对数据行数的统计或对某一栏有值的数据行数统计
MAX(字段名)取得一个表格栏最大的值
MIN(字段名)取得一个表格栏最小的值
SUM(字段名)把数据栏的值相加


引用以上函数的方法:
sql="select sum(filed) as 别名from 数据表where条件表达式"  //返回一个统计值

六 建立表和创建表

   CREATETABLE tb1 filed1类型1(长度), filed1 类型2(长度)……)
例:CREATETABLEtab01 (namevarchar (50), datetimedefaultnow ())

DROPTABLE数据表名称(永久性删除一个数据表)

 

七 创建数据库

   CREATE DATABASE database-name

八 删除数据库

   drop database dbname

*其它技巧

1、1=1,1=2的使用,在SQL语句组合时用的较多

“where 1=1” 是表示选择全部   “where 1=2”全部不选,
如:
if @strWhere !=''
begin
set @strSQL = 'select count(*) as Total from [' + @tblName + '] where ' + @strWhere
end
else
begin
set @strSQL = 'select count(*) as Total from [' + @tblName + ']'
end

我们可以直接写成
set @strSQL = 'select count(*) as Total from [' + @tblName + '] where 1=1 安定 '+ @strWhere

2、收缩数据库
--重建索引
DBCC REINDEX
DBCC INDEXDEFRAG
--收缩数据和日志
DBCC SHRINKDB
DBCC SHRINKFILE

3、压缩数据库
dbcc shrinkdatabase(dbname)

4、转移数据库给新用户以已存在用户权限
exec sp_change_users_login 'update_one','newname','oldname'
go

5、检查备份集
RESTORE VERIFYONLY from disk='E:"dvbbs.bak'

6、修复数据库
ALTER DATABASE [dvbbs] SET SINGLE_USER
GO
DBCC CHECKDB('dvbbs',repair_allow_data_loss) WITH TABLOCK
GO
ALTER DATABASE [dvbbs] SET MULTI_USER
GO

7、日志清除
SET NOCOUNT ON
DECLARE @LogicalFileName sysname,
        @MaxMinutes INT,
        @NewSize INT


USE     tablename             --
要操作的数据库名
SELECT @LogicalFileName = 'tablename_log', -- 日志文件名
@MaxMinutes = 10,               -- Limit on time allowed to wrap log.
        @NewSize = 1                  -- 你想设定的日志文件的大小(M)

-- Setup / initialize
DECLARE @OriginalSize int
SELECT @OriginalSize = size
FROM sysfiles
WHERE name = @LogicalFileName
SELECT 'Original Size of ' + db_name() + ' LOG is ' +
        CONVERT(VARCHAR(30),@OriginalSize) + ' 8K pages or ' +
        CONVERT(VARCHAR(30),(@OriginalSize*8/1024)) + 'MB'
FROM sysfiles
WHERE name = @LogicalFileName
CREATE TABLE DummyTrans
(DummyColumn char (8000) not null)


DECLARE @Counter   INT,
        @StartTime DATETIME,
        @TruncLog VARCHAR(255)
SELECT @StartTime = GETDATE(),
        @TruncLog = 'BACKUP LOG ' + db_name() + ' WITH TRUNCATE_ONLY'

DBCC SHRINKFILE (@LogicalFileName, @NewSize)
EXEC (@TruncLog)
-- Wrap the log if necessary.
WHILE     @MaxMinutes > DATEDIFF (mi, @StartTime, GETDATE()) -- time has not expired
      AND @OriginalSize = (SELECT size FROM sysfiles WHERE name = @LogicalFileName)
      AND (@OriginalSize * 8 /1024) > @NewSize
BEGIN -- Outer loop.
    SELECT @Counter = 0
    WHILE ((@Counter < @OriginalSize / 16) AND (@Counter < 50000))
      BEGIN -- update
        INSERT DummyTrans VALUES ('Fill Log')
        DELETE DummyTrans
        SELECT @Counter = @Counter + 1
      END  
    EXEC (@TruncLog)
END  
SELECT 'Final Size of ' + db_name() + ' LOG is ' +
        CONVERT(VARCHAR(30),size) + ' 8K pages or ' +
        CONVERT(VARCHAR(30),(size*8/1024)) + 'MB'
FROM sysfiles
WHERE name = @LogicalFileName
DROP TABLE DummyTrans
SET NOCOUNT OFF

8、说明:更改某个表
exec sp_changeobjectowner 'tablename','dbo'

9、存储更改全部表

CREATE PROCEDURE dbo.User_ChangeObjectOwnerBatch
@OldOwner as NVARCHAR(128),
@NewOwner as NVARCHAR(128)
AS

DECLARE @Name   as NVARCHAR(128)
DECLARE @Owner as NVARCHAR(128)
DECLARE @OwnerName as NVARCHAR(128)

DECLARE curObject CURSOR FOR
select 'Name'   = name,
'Owner'   = user_name(uid)
from sysobjects
where user_name(uid)=@OldOwner
order by name

OPEN curObject
FETCH NEXT FROM curObject INTO @Name, @Owner
WHILE(@@FETCH_STATUS=0)
BEGIN    
if @Owner=@OldOwner
begin
set @OwnerName = @OldOwner + '.' + rtrim(@Name)
exec sp_changeobjectowner @OwnerName, @NewOwner
end
-- select @name,@NewOwner,@OldOwner

FETCH NEXT FROM curObject INTO @Name, @Owner
END

close curObject
deallocate curObject
GO


10
、SQL SERVER中直接循环写入数据
declare @i int
set @i=1
while @i<30
begin
   insert into test (userid) values(@i)
   set @i=@i+1
end