SQL 函数、存储过程、游标与事务模板

1.标量函数：结果为一个单一的值，可包含逻辑处理过程。其中不能用getdate()之类的不确定性系统函数.

--标量值函数
-- ================================================
-- Template generated from Template Explorer using:
-- Create Scalar Function (New Menu).SQL
--
-- Use the Specify Values for Template Parameters 
-- command (Ctrl-Shift-M) to fill in the parameter 
-- values below.
--
-- This block of comments will not be included in
-- the definition of the function.
-- ================================================
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:   <Author,,Name>
-- Create date: <Create Date, ,>
-- Description: <Description, ,>
-- =============================================
CREATE FUNCTION <Scalar_Function_Name, sysname, FunctionName> 
(
-- Add the parameters for the function here
<@Param1, sysname, @p1> <Data_Type_For_Param1, , int>
)
RETURNS <Function_Data_Type, ,int>
AS
BEGIN
-- Declare the return variable here
DECLARE <@ResultVar, sysname, @Result> <Function_Data_Type, ,int>

-- Add the T-SQL statements to compute the return value here
SELECT <@ResultVar, sysname, @Result> = <@Param1, sysname, @p1>

-- Return the result of the function
RETURN <@ResultVar, sysname, @Result>

END

2.内联表值函数:返回值为一张表,仅通过一条SQL语句实现,没有逻辑处理能力.可执行大数据量的查询.

--内联表值函数

-- ================================================
-- Template generated from Template Explorer using:
-- Create Inline Function (New Menu).SQL
--
-- Use the Specify Values for Template Parameters 
-- command (Ctrl-Shift-M) to fill in the parameter 
-- values below.
--
-- This block of comments will not be included in
-- the definition of the function.
-- ================================================
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:   <Author,,Name>
-- Create date: <Create Date,,>
-- Description: <Description,,>
-- =============================================
CREATE FUNCTION <Inline_Function_Name, sysname, FunctionName> 
( 
-- Add the parameters for the function here
<@param1, sysname, @p1> <Data_Type_For_Param1, , int>, 
<@param2, sysname, @p2> <Data_Type_For_Param2, , char>
)
RETURNS TABLE 
AS
RETURN 
(
-- Add the SELECT statement with parameter references here
SELECT 0
)
GO

3.多语句表值函数:返回值为一张表,有逻辑处理能力,但仅能对小数据量数据有效,数据量大时,速度很慢.

--多语句表值函数

-- ================================================
-- Template generated from Template Explorer using:
-- Create Multi-Statement Function (New Menu).SQL
--
-- Use the Specify Values for Template Parameters 
-- command (Ctrl-Shift-M) to fill in the parameter 
-- values below.
--
-- This block of comments will not be included in
-- the definition of the function.
-- ================================================
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:   <Author,,Name>
-- Create date: <Create Date,,>
-- Description: <Description,,>
-- =============================================
CREATE FUNCTION <Table_Function_Name, sysname, FunctionName> 
(
-- Add the parameters for the function here
<@param1, sysname, @p1> <data_type_for_param1, , int>, 
<@param2, sysname, @p2> <data_type_for_param2, , char>
)
RETURNS 
<@Table_Variable_Name, sysname, @Table_Var> TABLE 
(
-- Add the column definitions for the TABLE variable here
<Column_1, sysname, c1> <Data_Type_For_Column1, , int>, 
<Column_2, sysname, c2> <Data_Type_For_Column2, , int>
)
AS
BEGIN
-- Fill the table variable with the rows for your result set

RETURN 
END
GO

4.游标:对多条数据进行同样的操作.如同程序的for循环一样.有几种循环方向控制,一般用FETCH Next.

--示意性SQL脚本

DECLARE @MergeDate Datetime 
DECLARE @MasterId Int 
DECLARE @DuplicateId Int 

SELECT @MergeDate = GetDate() 


DECLARE merge_cursor CURSOR FAST_FORWARD FOR SELECT MasterCustomerId, DuplicateCustomerId FROM DuplicateCustomers WHERE IsMerged = 0 
--定义一个游标对象[merge_cursor]
--该游标中包含的为:[SELECT MasterCustomerId, DuplicateCustomerId FROM DuplicateCustomers WHERE IsMerged = 0 ]查询的结果.

OPEN merge_cursor 
--打开游标
FETCH NEXT FROM merge_cursor INTO @MasterId, @DuplicateId 
--取数据到临时变量
WHILE @@FETCH_STATUS = 0 --系统@@FETCH_STATUS = 0 时循环结束
--做循环处理
BEGIN 
EXEC MergeDuplicateCustomers @MasterId, @DuplicateId 

UPDATE DuplicateCustomers 
SET 
IsMerged = 1, 
MergeDate = @MergeDate 
WHERE 
MasterCustomerId = @MasterId AND 
DuplicateCustomerId = @DuplicateId 

FETCH NEXT FROM merge_cursor INTO @MasterId, @DuplicateId 
--再次取值
END 

CLOSE merge_cursor 
--关闭游标
DEALLOCATE merge_cursor 
--删除游标

[说明:游标使用必须要配对,Open--Close,最后一定要记得删除游标.]

5.事务:当一次处理中存在多个操作,要么全部操作,要么全部不操作,操作失败一个,其他的就全部要撤销,不管其他的是否执行成功,这时就需要用到事务.

begin tran
update tableA
set columnsA=1,columnsB=2
where RecIs=1
if(@@ERROR <> 0 OR @@ROWCOUNT <> 1)
begin
rollback tran
raiserror( '此次update表tableA出错!!' , 16 , 1 ) 
return
end

insert into tableB (columnsA,columnsB) values (1,2)
if(@@ERROR <> 0 OR @@ROWCOUNT <> 1)
begin
rollback tran
raiserror( '此次update表tableA出错!!' , 16 , 1 ) 
return
end

end
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