SQL Server的使用笔记

SQL Server的使用笔记

一、比较复杂的update语句：update .. from 

update T_BuyMaterialReceiveStoreDetail

set QCID = a.QCID,

QCQty = isnull(a.QCQty,a.Qty),

QCPricePercent = isnull(a.QCPricePercent,1),

QCFailedQty = isnull(a.QCFailedQty,0),

QCWasteQty = isnull(a.QCWasteQty,0),

QCShortQty = isnull(a.QCShortQty,0),

QCPercent = isnull(a.QCPercent,1),

Note = a.Note,

DeterMineResult=a.DeterMineResult

from (select * from T_Temp_BuyMaterialReceiveStoreDetail

where OperateID = @OperateID

and OperateTime = @OperateTime

and QCID = QCID) a

where T_BuyMaterialReceiveStoreDetail.BuyID = a.BuyID

and T_BuyMaterialReceiveStoreDetail.MaterialItemID = a.MaterialItemID

and T_BuyMaterialReceiveStoreDetail.ReceiveID = a.ReceiveID

and T_BuyMaterialReceiveStoreDetail.StoreID = a.StoreID

and T_BuyMaterialReceiveStoreDetail.MaterialColorID = a.MaterialColorID

and T_BuyMaterialReceiveStoreDetail.MaterialSizeID = a.MaterialSizeID

and T_BuyMaterialReceiveStoreDetail.SaleID = a.SaleID

and T_BuyMaterialReceiveStoreDetail.StyleID = a.StyleID

 

二、判断varchar型的数据是否空

len(Note)= 0 

 

三、将数据库的表的表结构的ntext类型的字段改为nvarchar(max)

select 'alter table ' +  c.name+' alter column '+a.name+' nvarchar(max)' 

from sys.columns a

left join sys.types b on a.system_type_id = b.system_type_id and b.name='ntext'

left join sys.objects c on a.object_id = c.object_id and c.Type='U'

where b.name='ntext' and c.Type='U'

四、巧妙的将返回的所有行的记录以一行字符串的形式输出

 

DECLARE @STR VARCHAR(8000)

SELECT @STR = ISNULL(@STR,'')+salecode+char(13) FROM t_sale 

SELECT @STR 

五、处理bit的类型的数据不能max

max(cast(a.State as int))

六、对调数据库中的两行记录的某个字段的值

update T_ReportConfig

set Array = case

when ReportConfigID = 17 then (select Array from T_ReportConfig where  ReportConfigID=18)

else (select Array from T_ReportConfig where  ReportConfigID=17)

end

where ReportConfigID in (17,18)

个人解释：sql编译时，先计算了()中的值，所以巧妙的达到了交互两个值

七、delete exists

delete from A 

where exists(select * 

from B a

where A.Column = a.Column)

八、OBJECT_ID (Transact-SQL)

Returns the database object identification number of a schema-scoped object. 对象标识号

语法：

OBJECT_ID ( '[ database_name . [ schema_name ] . | schema_name . ] 

  object_name' [ ,'object_type' ] )

例子：

select count(1) from syscolumns where [id]=object_id('T_Operator') and [name]='OperatorID'

九、数据库中对象是否存在

1.表中的列

select count(1) from syscolumns where [id]=object_id('T_Operator') and [name]='OperatorID'

2.表

select count(*) from sysobjects 

where id = object_id(N'[T_Operator]') and OBJECTPROPERTY(id, N'IsUserTable') = 1

十、SqlServer字符串前加N

加上 N 代表存入数据库时以 Unicode 格式存储。

N'string' 表示string是个Unicode字符串

Unicode 字符串的格式与普通字符串相似，但它前面有一个 N 标识符（N 代表 SQL-92 标准中的国际语言 (National Language)）。

Unicode 常量确实有排序规则，主要用于控制比较和区分大小写

十一、OBJECTPROPERTY

http://msdn.microsoft.com/en-us/library/aa276849(v=sql.80).aspx

Returns information about objects in the current database