Stored procedures in sqlserver

• Stored in advance sql Program （ Database operation statement , Variable , Logic control statements, etc ）
• Save in SQL Server in
• By name and parameters , Return result .

Advantages of stored procedures ：

• Fast execution
• Allow modular programming
• Improve system security
• Reduce network traffic

System stored procedure

• The name of the system stored procedure is generally “sp_” start
• from SQLServer establish 、 Management and use
• Store in Resource In the database

sp_databases List all the databases on the server
sp_tables Returns the list of objects that can be queried in the current environment
sp_helptext Open another unencrypted stored procedure to view
Examples are as follows

execute sp_databases
exec sp_helptext sp_databases

Extending stored procedures

• Extended stored procedures are usually named with “xp_” start
• Using the editing language （ Such as C#） Created external stored procedures
• With DLL Forms exist alone

xp_cmdshell

• It can be executed DOS Some operations under the command
• You can return any output as a line

It is written as follows ：

EXEC xp_cmdshell DOS command [NO_OUTPUT]

Examples are as follows ：

USE master
GO
/*--- if xp_cmdShell Shut down as part of the server security configuration , Please use the following statement to enable ---*/
Exec sp_configure 'show advanced options ' , 1 -- Display advanced configuration information 
GO
RECONFIGURE -- Reconfiguration 
GO
exec sp_configure 'xp_cmdShell',1-- open xp_configure Options 
GO
REconfigure -- Reconfiguration 
/*--- Create database bankDB, Request to be kept in D:\bank---*/
Exec xp_cmdshell 'mkdir D:\bank', NO_OUTPUT -- Create folder D:\bank
-- Create database bankDB

User defined stored procedures

Parameterless stored procedure

Nonparametric stored procedure definition

CREATE PROC[ EDURE ] Stored procedure name
AS
SQL sentence
GO

Using the syntax of stored procedures ：
EXECUTE The process of
EXEC The process of

If the statement executing the stored procedure is the first statement in a batch statement , You may not specify
EXECUTE keyword .

Examples are as follows ：

 use MySchool
go
    create proc stuResult
    as
    
    ---- Find this Java OOP  The average score of the test and the information of the people who failed 


    --- Define variables to save the last exam time 

declare @maxDate datetime 




select @maxDate = MAX(ExamDate) from Result
  where SubjectId =(select SubjectId from Subject 
                    where SubjectName = 'Java OOP')
 
 
--- Calculate the average score 
select AVG(StudentResult) from Result
	where ExamDate = @maxDate
	and SubjectId = (select SubjectId from Subject 
                    where SubjectName = 'Java OOP') 
-- Check the list of students who failed the exam 
select * from Student
		where StudentNo =(
	select StudentNo from Result
	where SubjectId =  (select SubjectId from Subject 
                    where SubjectName = 'Java OOP') 
    and ExamDate = @maxDate  
    and StudentResult < 80
    ) 
    go                                 

Calling a parameterless stored procedure

Exec stuResult
    

Stored procedures with parameters

Create stored procedure syntax with parameters

CREAT PROC[EDURE] Stored procedure name
@ Parameters 1,@ Parameters 2,…,@ Parameters n
AS
SQL sentence
GO

Execute stored procedure syntax

EXECUTE The process of Parameters
EXEC The process of Parameters

Stored procedure parameters ：

• Input parameters ： Pass in the value to the stored procedure
• Output parameters ： Stored procedure output value , Use output keyword

Execute stored procedures

EXEC The process of ’ value ', value

or

EXEC Stored procedure name Parameters 1 = ’ ’ , Parameters 2 = ’ ’

Two ways , One is to use the form of key value pairs to pass , One is to pass parameters directly in order .

Examples are as follows ：

use MySchool
go

 
create proc proc_stuResultParam
	@subject varchar(10),
	@score int
    as
    
    ---- Find this Java OOP  The average score of the test and the information of the people who failed 


    --- Define variables to save the last exam time 
declare @maxDate datetime 





select @maxDate = MAX(ExamDate) from Result
  where SubjectId =(select SubjectId from Subject 
                    where SubjectName = @subject)
 
 
--- Calculate the average score 
select AVG(StudentResult) from Result
	where ExamDate = @maxDate
	and SubjectId = (select SubjectId from Subject 
                    where SubjectName = @subject) 
-- Check the list of students who failed the exam 
select * from Student
		where StudentNo in(
	select StudentNo from Result
	where SubjectId =  (select SubjectId from Subject 
                    where SubjectName = @subject) 
    and ExamDate = @maxDate  
    and StudentResult < @score 
    ) 
    go  
    --  Calling a parameter stored procedure 
    exec dbo.proc_stuResultParam 'Java OOP',94
    
    exec dbo.proc_stuResultParam @subject ='C# oop',@score =80

You can also specify the default value when declaring formal parameters. The default value will be overridden by the new parameter .
When declaring parameters, the parameters with default values should be declared later , Otherwise, you need to add... Before the parameter when passing in the parameter default keyword .

Output parameters

• When using, you must add... After the attribute output Keyword to indicate that the parameter is an output parameter
• When receiving an outgoing result, declare a new parameter for receiving

Examples are as follows ：

use MySchool
go

 
create proc proc_stuResultParam
	@subject varchar(10), -- Input parameters 
	@score int = 60,
	@count int output -- Output parameters 
    as
    
    ---- Find this Java OOP  The average score of the test and the information of the people who failed 


    --- Define variables to save the last exam time 
declare @maxDate datetime 





select @maxDate = MAX(ExamDate) from Result
  where SubjectId =(select SubjectId from Subject 
                    where SubjectName = @subject)
 
 
--- Calculate the average score 
select AVG(StudentResult) from Result
	where ExamDate = @maxDate
	and SubjectId = (select SubjectId from Subject 
                    where SubjectName = @subject) 
-- Check the list of students who failed the exam 
select * from Student
		where StudentNo in(
	select StudentNo from Result
	where SubjectId =  (select SubjectId from Subject 
                    where SubjectName = @subject) 
    and ExamDate = @maxDate  
    and StudentResult < @score 
    ) 
-- Count the number of people who failed 

select @count = count(StudentNo) from Result
	where SubjectId  =  (select SubjectId from Subject 
                    where SubjectName = @subject) 
    and ExamDate = @maxDate  
    and StudentResult < @score 
    go  
    declare @c int 
    --  Calling a parameter stored procedure 
   --exec dbo.proc_stuResultParam 'Java OOP',80, @c output
   --select @c
    
   exec dbo.proc_stuResultParam @subject ='C# oop',@count = @c output

It can also be used in the same way return , But before you receive the data that's coming out , To receive from a newly declared parameter return The parameters come out , The parameters received in this way are just return The parameters passed out .
Examples are as follows ：

use MySchool
go

 
create proc proc_stuResultParam
	@subject varchar(10), -- Input parameters 
	@score int = 60,
	@count int output -- Output parameters 
    as
    
    ---- Find this Java OOP  The average score of the test and the information of the people who failed 


    --- Define variables to save the last exam time 
declare @maxDate datetime 





select @maxDate = MAX(ExamDate) from Result
  where SubjectId =(select SubjectId from Subject 
                    where SubjectName = @subject)
 
 
--- Calculate the average score 
select AVG(StudentResult) from Result
	where ExamDate = @maxDate
	and SubjectId = (select SubjectId from Subject 
                    where SubjectName = @subject) 
-- Check the list of students who failed the exam 
select * from Student
		where StudentNo in(
	select StudentNo from Result
	where SubjectId =  (select SubjectId from Subject 
                    where SubjectName = @subject) 
    and ExamDate = @maxDate  
    and StudentResult < @score 
    ) 
-- Count the number of people who failed 

select @count = count(StudentNo) from Result
	where SubjectId  =  (select SubjectId from Subject 
                    where SubjectName = @subject) 
    and ExamDate = @maxDate  
    and StudentResult < @score 
   -- The stored procedure returns the highest score 
   declare @max int = 0
   select @max = max(StudentResult) from Result
	where SubjectId  =  (select SubjectId from Subject 
                    where SubjectName = @subject) 
    and ExamDate = @maxDate  
    return @max
    go  
    declare @c int
   
    --  Calling a parameter stored procedure 
   --exec dbo.proc_stuResultParam 'Java OOP',80, @c output
   --select @c
    declare @MaxReturnParam int -- By receiving return The value returned by the 
   exec @MaxReturnParam = dbo.proc_stuResultParam @subject ='C# oop',@count = @c output
   select @MaxReturnParam

Custom error message

Use RAISERROR From defining error messages ：
RAISERROR（msg_id| msg_str,severity, state WITH option[,…n]）
msg_id : stay sysmessages User defined error messages are specified in the system table
msg_str: User defined specific information , The longest 255 Characters
severity: Define the severity level . Users can use the level of 0~18 level

• 0~10： It won't jump to catch
• 11-19： Get into catch
• 20-： Terminate the database connection

state： State of an error ,1 To 127 Between the value of the
option： Indicates whether to log errors to the server error day
Examples are as follows ：`

declare @age int 
set @age =1000



if(@age>=0 and @age<=100)
print @age
else
-- Text , error level （0~18 Between ）, state （1~127）
raiserror(' Age should be entered 0~100 Between ',16,1)