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Stored procedure and stored function in Oracle

2022-07-05 01:42:00 【Milk coffee 13】

One 、 stored procedure

1.1、 The introduction of stored procedure

stored procedure （Stored Procedure） In a large database system , A group of SQL Statements set , After compilation, it is directly stored in the database , The user calls the name of the specified stored procedure and passes the corresponding parameters （ If the stored procedure has parameters ） To execute it. . Stored procedure is an important object in database , Any well-designed database application has stored procedures .

1.2、 Advantages and disadvantages of stored procedures

stored procedure (Stored Produce) The advantages of
Serial number	stored procedure 【Stored Produce】 The advantages of
1	Stored procedure can make program execution more efficient 、 Better security , Because after the process is created and saved, it has been compiled and stored in the database , And write directly sql Statements need to be parsed by the analyzer before execution, so the process is more efficient , And write directly sql Statement may cause some security problems , Such as ：sql Inject etc.
2	The establishment of stored procedures consumes little system resources （ This is because stored procedures are only executed when called ）
3	Stored procedures can be used to reduce network traffic （ This is because the code of the stored procedure is directly stored locally in the database , Call directly , Instead of writing a lot of sql Code for statement ）
4	Stored procedures enable you to enhance the reuse of execution plans
5	High maintainability （ This is because updating stored procedures is usually better than changing 、 Testing and redeploying assemblies takes less time and effort ）
6	The code is concise and consistent （ A stored procedure can be used in different locations of the application code ）
7	Enhance security （ ① By granting access to stored procedures to users （ Not based on tables ） Access rights of , They can provide access to specific data ; ② Improve code security , prevent SQL Inject ; ③SqlParameter Class specifies the data type of stored procedure parameters , As part of a deep defensive strategy , You can verify the value type provided by the user ）

stored procedure (Stored Produce) Deficiency
Serial number	stored procedure 【Stored Produce】 Deficiency
1	Extensive use of stored procedures , It's going to put a lot of pressure on the server

1.3、 Creation syntax of stored procedure

Parametric 3 Types
Serial number	Parameter type description
1	IN Is the default mode of the parameter , This pattern is When the program is running, it already has a value , The value in the program body does not change
2	OUT Pattern Defined parameters can only be assigned inside the procedure body , Indicates that the parameter can pass a value to the callback with its procedure
3	IN OUT Express This parameter can pass a value to this procedure , You can also pass a certain value

// Basic grammar 
create [or replace] procedure  Stored procedure name 
( Parameter name   in|out  Parameter type , Parameter name   in|out  Parameter type ) is|as

- -  Variable declaration part 

begin

- -  Business logic part 

end;


// Detailed grammatical content 
create [or replace] procedure  Stored procedure name 
(param1 in type,param2 out type) is|as

    Variable 1  type （ Range of values ）;
    Variable 2  type （ Range of values ）;

begin
   select count(*) into  Variable 1 from  surface A where Name =param1;
   if ( Judge the condition ) then
        select  Name  into  Variable 2 from  surface A where Name =param1;
        dbms_output.Put_line(' Print information ');
   elsif ( Judge the condition ) then
        dbms_output.Put_line(' Print information ');
   else
        raise  Exception names （NO_DATA_FOUND）;
   end if;
exception
   when others then
        rollback;
end;

1.4、 Syntax for executing stored procedures

Method 1 ：

// Execute stored procedure syntax 1
CALL  Stored procedure name ( Parameters 1, Parameters 2);

// Example of executing a stored procedure 
CALL CACULATESALARY(1,5000);

Method 2 ：

// Execute stored procedure syntax 2
BEGIN
 Stored procedure name ( Parameters 1, Parameters 2);
END;


// Example of executing a stored procedure 
BEGIN
caculatesalary(1,5000);
END;

1.5、 Examples of stored procedures

Example 1： To enter the employee number and the amount of salary increase, first view the original salary ; Then update the employee's salary , Then print it out and check ; Finally, if the update fails, you need to rollback .

The contents of the table are as follows ：

The stored procedure is as follows ：

CREATE OR REPLACE PROCEDURE CaculateSalary 
(peopleNumber in NUMBER,needIncreaseSalaryNumber in NUMBER)
AS

TotalSalary NUMBER:=0;

BEGIN
	
	-- Get the current salary 
	SELECT SALARY INTO TotalSalary from PEOPLE WHERE PEOPLE.ID=peopleNumber;
	-- The salary before outputting a salary 
	dbms_output.put_line(' The salary before the salary rise is ：'||TotalSalary);
	-- Salary after salary increase 
	UPDATE PEOPLE SET SALARY=(TotalSalary+needIncreaseSalaryNumber) WHERE ID=peopleNumber;
  -- The salary after outputting a salary 
	dbms_output.put_line(' After the salary increase, the salary is ：'||(TotalSalary+needIncreaseSalaryNumber));
	-- Commit transaction 
	commit;
	
	-- If an exception occurs, rollback 
	EXCEPTION
	 WHEN OTHERS THEN
	 rollback;
	 dbms_output.put_line(' Execute rollback operation for abnormal salary increase ');
END;

Example 2： You want to pass in parameters , Then pass the content through this parameter

CREATE OR REPLACE procedure testInuptOutput
(message in out varchar2)
-- When you want to bring in value , Want to take value out again , It can be used in out
as

begin
  dbms_output.put_line(' The current input is ：'||message); -- The output is the value carried in 
  message:=' I am the processed value '||998;
end;

Two 、 Storage function

2.1、 Introduction to storage function

Storage function （Stored Function） It is saved in the database after creation , And encapsulated in oracle A section in the server has been completed plsql code snippet .

2.2、 Characteristics of storage functions

Storage function (Stored Function) Characteristics
Serial number	Characteristics of storage functions
1	Automatically load when the database starts
2	Function has no parameter input and output
3	Function must have a return value
4	When calling a function, you must use its return value
5	The storage function can be in sql Use in statement , It can also be in plsql Use in

2.3、 Storage function creation syntax

Parametric 3 Types
Serial number	Parameter type description
1	IN Is the default mode of the parameter , This pattern is When the program is running, it already has a value , The value in the program body does not change
2	OUT Pattern Defined parameters can only be assigned inside the procedure body , Indicates that the parameter can pass a value to the callback with its procedure
3	IN OUT Express This parameter can pass a value to this procedure , You can also pass a certain value

// Basic syntax for storing functions 
create [for replace] function  The name of the storage function ( Parameter name  in|out  Parameter type , Parameter name  in|out  Parameter type ）

return  Parameter type 

is | as

begin


end;




// The detailed syntax of the storage function 
Create [or replace] function  The name of the function （ Parameter name  in|out  Parameter type , Parameter name  in|out  Parameter type ,...）

Return  Result variable data type 

Is | as

 Variable declaration part ;

Begin

 Logical part ;

Return  Outcome variable ;

[exception  Exception handling part ]

End;

 Be careful ：end hinder ; Cannot cancel . The parameter list defaults to the input type  in

2.4、 Syntax for executing storage functions

// Execute the storage function method 1（ Put in expression ）

SELECT  The name of the function ( Parameters )  FROM dual;



// Execute the storage function method 1 Example 
SELECT TIMEGROUP(TO_DATE('2022-02-12 17:30:36', 'yyyy-MM-dd hh24:mi:ss'))handleTime FROM dual;

// Execute the storage function method 2

declare 

  Variable name   type ;

begin

 -- Assign storage function results to variables 
  Variable name := Store function name 
 -- Print variable results 
 dbms_output.put_line( Variable name );

end;



// Execute the storage method 2 Example 
declare 

result varchar(16);

begin

 result:= TIMEGROUP(TO_DATE('2022-02-12 17:30:36', 'yyyy-MM-dd hh24:mi:ss'));

 dbms_output.put_line(result);

end;

2.5、 Storage function example

Example ： Group dates （ namely ： The group with an interval of one hour starting from half an hour

①【 such as ：2022-02-13 07:30:00 Until 2022-02-13 08:29:59】 Of is classified as 2022-02-13 08:30:00

②【 such as ：2022-02-13 08:30:00 Until 2022-02-13 09:29:59】 Of is classified as 2022-02-13 09:30:00）

The storage function is as follows ：

CREATE OR REPLACE FUNCTION TimeGroup(inputDate IN DATE) RETURN VARCHAR2
AS
result VARCHAR(16):='';
input_yyyy_MM_dd_hh24 VARCHAR(13):=to_char(inputDate,'yyyy-MM-dd hh24');
tmp_timegroup DATE:=TO_DATE(input_yyyy_MM_dd_hh24||'30:00','yyyy-MM-dd hh24:mi:ss');


BEGIN
  IF inputDate>=tmp_timegroup 
	THEN result:=SUBSTR(TO_CHAR((tmp_timegroup+1/24),'yyyy-MM-dd hh24:mi:ss'),0,16);
	ELSE result:=SUBSTR(TO_CHAR((tmp_timegroup),'yyyy-MM-dd hh24:mi:ss'),0,16);
	END IF;
	RETURN result;
END;

3、 ... and 、 The similarities and differences between stored procedures and stored functions

The similarities between stored procedures and stored functions
Serial number	The similarities between stored procedures and stored functions
1	Create grammatical structures similar to , Can carry multiple incoming and outgoing parameters
2	It's all a compilation , Multiple runs
3	You can use 【in/ out /in out】 The parameters of the three modes

The difference between stored procedure and stored function
stored procedure	Storage function
Used to complete specific operations in the database （ Or task ）【 The process is usually designed to find several operation results , Complete a series of data processing , Or various operations unrelated to calculation 】（ such as ： Insert 、 to update 、 Delete and other operations ）	For specific data operations 【 Just to get a value 】（ such as ： classified 、 grouping ）
Program header use 【Procedure】 Statement	Program header use 【Function】 Statement
No return type is required for program header declaration	The return type must be described when declaring the program header , And must be PL/SQL The block contains a valid return sentence
Can be used as an independent PL/SQL Statement to execute	Cannot execute independently , Must be called as part of the expression
Can pass out /in out Returns zero or more values	① adopt return Statement returns a value , And the return value must be consistent with the declared content ; ② It can also be done through out Type parameters bring out variables
SQL sentence （DML or SELECT） Cannot call stored procedures in	SQL sentence （DML or SELECT） Storage functions can be called in