数据库优化整合

1、OR语句可能会破坏索引的作用引发表扫描，可以可以分解成Union语句。例如：
         select a.cola,b.colb from taba a inner join tabb b on a.xxx=b.sss or a.ttt=b.yyy
      可以转化为
         select a.cola,b.colb from taba a inner join tabb b on a.ttt=b.yyy
               union all
         select a.cola,b.colb from taba a inner join tabb b on a.ttt=b.yyy
      不过具体情形还是要看执行计划。
2、TRUNCATE TABLE

Removes all rows from a table without logging the individual row deletions. TRUNCATE TABLE is functionally the same as the DELETE statement with no WHERE clause; however, TRUNCATE TABLE is faster and uses fewer system and transaction log resources.

TRUNCATE TABLE 

    [ { database_name.[ schema_name ]. | schema_name . } ]

    table_name

[ ; ]

3、SQL中cross join，left join，right join ，full join，inner join 的区别

cross join 是笛卡儿乘积就是一张表的行数乘以另一张表的行数
left join 第一张表的连接列在第二张表中没有匹配是,第二张表中的值返回null
right join 第二张表的连接列在第一张表中没有匹配是,第一张表中的值返回null
full join 返回两张表中的行 left join+right join
inner join 只返回两张表连接列的匹配项

4、SQL中使用cast转化datetime为varchar时会丢失秒，最好使用convert， CONVERT(data_type,expression[,style])，最后那个style变量就是在转换datetime时使用的。

style数字在转换时间时的含义如下

-------------------------------------------------------------------------------------------------
Style(2位表示年份) | Style(4位表示年份) | 输入输出格式
-------------------------------------------------------------------------------------------------
- | 0 or 100 | mon dd yyyy hh:miAM(或PM)
-------------------------------------------------------------------------------------------------
1 | 101 | mm/dd/yy
-------------------------------------------------------------------------------------------------
2 | 102 | yy-mm-dd
-------------------------------------------------------------------------------------------------
3 | 103 | dd/mm/yy
-------------------------------------------------------------------------------------------------
4 | 104 | dd-mm-yy
-------------------------------------------------------------------------------------------------
5 | 105 | dd-mm-yy
-------------------------------------------------------------------------------------------------
6 | 106 | dd mon yy
-------------------------------------------------------------------------------------------------
7 | 107 | mon dd,yy
-------------------------------------------------------------------------------------------------
8 | 108 | hh:mm:ss
-------------------------------------------------------------------------------------------------
- | 9 or 109 | mon dd yyyy hh:mi:ss:mmmmAM(或PM)
-------------------------------------------------------------------------------------------------
10 | 110 | mm-dd-yy
-------------------------------------------------------------------------------------------------
11 | 111 | yy/mm/dd
-------------------------------------------------------------------------------------------------
12 | 112 | yymmdd
-------------------------------------------------------------------------------------------------
- | 13 or 113 | dd mon yyyy hh:mi:ss:mmm(24小时制)
-------------------------------------------------------------------------------------------------
14 | 114 | hh:mi:ss:mmm(24小时制)
-------------------------------------------------------------------------------------------------
- | 20 or 120 | yyyy-mm-dd hh:mi:ss(24小时制)
-------------------------------------------------------------------------------------------------

- | 21 or 121 | yyyy-mm-dd hh:mi:ss:mmm(24小时制)

列出所有存储过程

SELECT * FROM SysObjects WHERE [xtype] = 'P'

查询存储过程的内容
EXEC Sp_HelpText '存储过程名'

查询空字符串
SELECT SPACE(空字符个数)

查看某个对象的全部依赖情况

SELECT distinct so.name
FROM syscomments sc
INNER JOIN sysobjects so ON sc.id = so.id
WHERE charindex('Object_Name', text) > 0

Select 赋值

select @counts=rowsCount from #tempRowCount

SQL引擎会遍历查询返回的数据，每条记录赋一次值，@counts的结果是查询返回的最后一条记录的值。

Delete Top

Delete top (1000) from table

可能的话，将表中所有的列都显示的声明为 NOT NULL，并且为丢失的或未知的项定义默认值。

取整函数:

上取整ceiling() 例如:ceiling(4.1) 返回值为5

下取整floor() 例如： floor(4.9) 返回值4

Get Table Space Status: sp_spaceused @TableName

Grant/Revoke

Attach DB By Script(you can name for the new DB):

CREATE DATABASE ASGDMbck ON
( FILENAME = N'G:\Data\ASGDM.mdf' ),
( FILENAME = N'G:\Data\ASGDM_1.ndf'),
( FILENAME = N'G:\Data\ASGDM_2.ldf')
FOR ATTACH

你不能在进程中看到SQLServer实际占得内存，需要到性能查看器中去看。

数据库优化整合

Find out which procedures are set to execute as specific user :

select object_name(object_id) from sys.sql_modules where execute_as_principal_id = user_id('alice')

Measuring the Run Time of Queries

DBCC DROPCLEANBUFFERS;
DBCC FREEPROCCACHE;

SET Statistics IO on
set statistics time on

exec spRptPonToolVerticalData_Adc2
@VerticalKey='194',
@Sites='bing.com',
@StartDate='Mar 1 2010 12:00AM',
@EndDate='May 30 2010 12:00AM',
@DateType='D',
@Alias='admin',
@ActionEntry='Ribbon'

set statistics time off
SET Statistics IO off