Stored procedures and functions

stored procedure ( Behavior oriented )

stored procedure （Stored Procedure） In a large database system , A group of SQL Statements set （pl/sql Subroutines ）, It's stored in a database , Once compiled, it's permanent , The user specifies the name of the stored procedure and gives the parameters （ If the stored procedure has parameters ） To execute it. .

Create stored procedure

One 、 Grammar format

create [or replace] procedure  Stored procedure name [( Parameter list  [in|out|in out]  Parameter data type )]
{
   is|as}
	 Declaration part ;
begin
	pl/sql Code block ;
exception
	 Exception handling statements ;
end;

• or replace Indicates that if there is a stored procedure with the same name, it will overwrite , If not, create
• Note that the formal parameter data type cannot be given specific precision, that is, it cannot be given varchar2(21) After （21） part

Two 、 Parameterless stored procedure

create or replace procedure p1 is
begin
	dbms_output.put_line('hello world');
end;

stay vs code The results after running in are as follows ：

3、 ... and 、 Stored procedures with parameters

• in—— Enter the storage function from the outside , And cannot be changed by stored procedures ( In a stored procedure, it is similar to a constant being processed )
  （1） Error model -1（ Give... In the stored procedure in Type parameter assignment ）

create or replace procedure p1(a IN NUMBER) is
begin
	-- The statement is not allowed 
	a:=1;
	-- Print a
	dbms_output.put_line(a);
end;

（2） Correct demonstration

-- Receive an employee number , Output employee name and employee position 
create OR REPLACE PROCEDURE p1(v_empno IN EMP.EMPNO%TYPE)
IS
	-- Declare a variable 
	A EMP%ROWTYPE;
BEGIN
	-- assignment 
	SELECT * INTO A FROM EMP WHERE EMPNO=v_empno;
	-- Output 
	dbms_output.put_line(' Name of employee ：'||a.ename||',  Employee position ：'||a.job);
END;

• out—— From stored procedure to external pl/sql Block , Can be changed by relevant contents in the stored procedure ( It can be seen as a variable thrown from a stored procedure ),out Variables must have corresponding variables externally

-- Throw the stored procedure variable value 
create OR replace PROCEDURE p1(n OUT VARCHAR2) IS
	a VARCHAR2(200):='hello world';
BEGIN
	n:=a;
END;

• in out—— In and out , Both external program blocks and internal stored procedures can be changed

---- According to the department number entered by the user , Output department related information 
create OR replace PROCEDURE p1(n IN OUT DEPT%ROWTYPE) IS
BEGIN
	SELECT * INTO n FROM DEPT WHERE DEPTNO=n.DEPTNO;
END;
/
-- call 
DECLARE
	n DEPT%ROWTYPE;
BEGIN
	n.DEPTNO:=& Please enter the department number ;
	-- Note that the parameter here is n instead of n.deptno
	p1(n);
	dbms_output.put_line(n.DEPTNO||', '||n.dname||', '||n.loc);
END;

Calling stored procedure

One 、pl/sql Call in

begin
-- Stored procedure call with parameters 
 Stored procedure name ( Actual parameters 1, Actual parameters 2,..., Actual parameters n);
-- Stored procedure calls without parameters 
 Stored procedure name ;
 Stored procedure name ();
end;

Two 、call call
The key codes are as follows ：

--call There is a special point ： Even if there is no parameter passing in the stored procedure, after the name of the stored procedure () Still cannot be omitted 
call  Stored procedure name ();

3、 ... and 、execute/exec call （cmd Window ）
(1)win+R Open the command prompt to log in sqlplus

(2) open serveroutput service , The code is as follows ：

set serveroutput on;

(3) Input exec/execute Stored procedure name （）;

Delete stored procedure

drop procedure  Stored procedure name ;

Other users use other stored procedures

（1） Log in to the stored procedure owner account , Grant user permission to use this process , The statement is as follows

grant execute on  Stored procedure name  to  user name ;

• The user applies the stored procedure owner account when calling this function . Stored procedure name ; for example scott.p1
• Withdraw permission to use revoke…from… Sentence can be used

function （ Pay attention to the results ）

Functions can be understood as special must have return Statement stored procedure

Create a function

One 、 Grammar format

create [or replace] function  Function name ( Shape parameter  [in|out|in out]  Parameter data type ) return  Return value data type 
is
	 Declaration part ;
begin
	pl/sql Code block ;
exception
	 exception handling ;
end;

Two 、 Parameterless function

create or replace function demo return varchar2
is
begin
	return 'Hello World';
end;

3、 ... and 、 Functions with parameters ( Similar to stored procedures , I won't repeat , Relevant examples are given as follows )

• in

-- Output user input 
create or replace function demo(a IN VARCHAR2) return varchar2
is
begin
	return a;
end;

• out

-- Throw the value in the function (return It can also be regarded as a out Parameters )
create or replace function demo(a OUT NUMBER) return NUMBER
is
b NUMBER:=3;
begin
	a:=b;
	return a;
end;

• in out

-- Enter the employee number and return the employee name 
create or replace function demo(a IN OUT EMP%ROWTYPE) return EMP%ROWTYPE
is
begin
	SELECT * INTO a FROM EMP WHERE EMPNO=a.EMPNO;
	return a;
end;
/
-- call 
DECLARE
	-- Carrying formal parameter variables 
	q EMP%ROWTYPE;
	-- Carrying function variables 
	e EMP%ROWTYPE;
BEGIN
	q.EMPNO:=& Please enter employee number ;
	e:=DEMO(A  => q /*OUT NUMBER*/);
	dbms_output.put_line(q.ename);
END;

Call function

• sql Call in

select  Function name ( Argument list ) from dual;

• pl/sql Call in

-- Because the function must have return Then we can treat the function as a value 
declare
	 Carrying function variables  return Return value data type ;
begin
	 Carrying function variables := Function name ( Argument list );
	-- What's printed here is return Return value content 
	dbms_output.put_line( Carrying function variables );
end;

Delete function

drop function  Function name ;

View all stored procedures and functions under the current user

SELECT * FROM USER_PROCEDURES;