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Create View with Parameter

From the title of this post you guess that oracle give us capability to create view with parameter, but this is wrong, don't think good of oracle to give you this capability as straight forward.

I have workaround to do this capability by the following techniques

1-virtual private database context
2-global package variable
3-Lookup Tables

#1 Virtual Private Database Context

I will use in where clause SYS_CONTEXT function as parameter to filter data of the query of the view.

First step is creating context that will handle session variables

 CREATE OR REPLACE CONTEXT MY_CTX USING CTX_PKG 

 ACCESSED GLOBALLY; 

Second I will create CTX_PKG package that context will use it to handle session parameters.

The package contains three procedures

a-SET_SESSION_ID to set unique id for every session I will use in my context.

b-CLEAR_SESSION to clear session from my context.

c-SET_CONTEXT to set variable value in my context.

Package Specification

 CREATE OR REPLACE PACKAGE CTX_PKG 

 IS 

   PROCEDURE SET_SESSION_ID (IN_SESSION_ID VARCHAR2); 

   PROCEDURE CLEAR_SESSION (IN_SESSION_ID VARCHAR2); 

   PROCEDURE SET_CONTEXT (IN_NAME VARCHAR2, IN_VALUE VARCHAR2); 

 END CTX_PKG; 

Package Body

 CREATE OR REPLACE PACKAGE BODY CTX_PKG 

 IS 

   GC$SESSION_ID  VARCHAR2 (100); 

   PROCEDURE SET_SESSION_ID (IN_SESSION_ID VARCHAR2) 

   IS 

   BEGIN 

    GC$SESSION_ID := IN_SESSION_ID; 

    DBMS_SESSION.SET_IDENTIFIER (IN_SESSION_ID); 

  END; 

   PROCEDURE CLEAR_SESSION (IN_SESSION_ID VARCHAR2) 

   IS 

   BEGIN 

    DBMS_SESSION.SET_IDENTIFIER (IN_SESSION_ID); 

    DBMS_SESSION.CLEAR_IDENTIFIER; 

   END; 

   PROCEDURE SET_CONTEXT (IN_NAME VARCHAR2, IN_VALUE VARCHAR2) 

   IS 

   BEGIN 

    DBMS_SESSION.SET_CONTEXT ('MY_CTX', 

                 IN_NAME, 

                 IN_VALUE, 

                 USER, 

                 GC$SESSION_ID); 

   END; 

 END CTX_PKG; 

Now let's test context and my package

 BEGIN 

   CTX_PKG.SET_SESSION_ID (222); 

   CTX_PKG.SET_CONTEXT ('my_name', 'Mahmoud A. El-Sayed'); 

   CTX_PKG.SET_CONTEXT ('my_age', '26 YO'); 

 END; 

Now I set two context variable my_name, my_age
to query this variable I will use SYS_CONTEXT function

 SELECT SYS_CONTEXT ('MY_CTX', 'my_name'), SYS_CONTEXT ('MY_CTX', 'my_age') 

  FROM DUAL; 

The output will be

After insuring that my context and package working true let's now create view on table EMP to get employee in department at SCOTT schema

 CREATE OR REPLACE VIEW EMP_IN_DEPRATMENT 

 AS 

   SELECT * 

    FROM EMP 

   WHERE DEPTNO = SYS_CONTEXT ('MY_CTX', 'deptno'); 

to filter view by employees in department 20 only you should execute this PLSQL block first

 BEGIN 

   CTX_PKG.SET_SESSION_ID (222); 

   CTX_PKG.SET_CONTEXT ('deptno', '20'); 

 END; 

Now lets create select statement against EMP_IN_DEPARTMENT view and see the result

 SELECT * FROM EMP_IN_DEPRATMENT; 

The output result is like below

#2 Global Package Variables

I will use in where clause global package variables as parameter to filter data of the query of the view.

I will create package that hold every global variables which I will use it as parameters in view.

Package Specification

CREATE OR REPLACE PACKAGE GLB_VARIABLES

IS

   GN$DEPTNO   EMP.DEPTNO%TYPE;

   PROCEDURE SET_DEPTNO (

      IN_DEPTNO EMP.DEPTNO%TYPE);

   FUNCTION GET_DEPTNO

      RETURN EMP.DEPTNO%TYPE;

END;

Package Body

 CREATE OR REPLACE PACKAGE BODY GLB_VARIABLES  

 IS 

   PROCEDURE SET_DEPTNO ( 

    IN_DEPTNO EMP.DEPTNO%TYPE) 

   IS 

   BEGIN 

    GN$DEPTNO := IN_DEPTNO; 

   END; 

   FUNCTION GET_DEPTNO 

    RETURN EMP.DEPTNO%TYPE 

   IS 

   BEGIN 

    RETURN GN$DEPTNO; 

   END; 

 END; 

Let's now create view filter its data by global variables in GLBL_VARIABLES package

 CREATE OR REPLACE VIEW EMP_IN_DEPRATMENT2 

 AS 

   SELECT * 

    FROM EMP 

   WHERE DEPTNO =GLB_VARIABLES.GET_DEPTNO; 

Now lets create select statement against EMP_IN_DEPARTMENT2 view and see the result

 EXEC GLB_VARIABLES.SET_DEPTNO(20);

 SELECT * FROM EMP_IN_DEPRATMENT2; 

The output result is like below

 

3-Lookup Tables

another solution is to create lockup table for storing view parameters on it and build view based on the data stored in lockup table.
This solution is straight forward solution so no need to make demo for this solution to make post shortly as possible

https://mahmoudoracle.blogspot.com/2012/06/create-view-with-parameter.html

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