How to Fetch Data Using Cursors in Packages and Procedures

How to Fetch Data Using Cursors in Packages and Procedures

Fetching Data

The following package defines a PL/SQL cursor variable type Emp_val_cv_type, and two procedures. The first procedure, Open_emp_cv, opens the cursor variable using a bind variable in the WHERE clause. The second procedure, Fetch_emp_data, fetches rows from the Emp_tab table using the cursor variable.

CREATE OR REPLACE PACKAGE Emp_data AS
TYPE Emp_val_cv_type IS REF CURSOR RETURN Emp_tab%ROWTYPE;
PROCEDURE Open_emp_cv (Emp_cv IN OUT Emp_val_cv_type,
Dept_number IN INTEGER);
PROCEDURE Fetch_emp_data (emp_cv IN Emp_val_cv_type,
emp_row OUT Emp_tab%ROWTYPE);
END Emp_data;

CREATE OR REPLACE PACKAGE BODY Emp_data AS
PROCEDURE Open_emp_cv (Emp_cv IN OUT Emp_val_cv_type,
Dept_number IN INTEGER) IS
BEGIN
OPEN emp_cv FOR SELECT * FROM Emp_tab WHERE deptno = dept_number;
END open_emp_cv;
PROCEDURE Fetch_emp_data (Emp_cv IN Emp_val_cv_type,
Emp_row OUT Emp_tab%ROWTYPE) IS
BEGIN
FETCH Emp_cv INTO Emp_row;
END Fetch_emp_data;
END Emp_data;


The following example shows how to call the Emp_data package procedures from a PL/SQL block:

DECLARE
-- declare a cursor variable
Emp_curs Emp_data.Emp_val_cv_type;
Dept_number Dept_tab.Deptno%TYPE;
Emp_row Emp_tab%ROWTYPE;

BEGIN
Dept_number := 20;
-- open the cursor using a variable
Emp_data.Open_emp_cv(Emp_curs, Dept_number);
-- fetch the data and display it
LOOP
Emp_data.Fetch_emp_data(Emp_curs, Emp_row);
EXIT WHEN Emp_curs%NOTFOUND;
DBMS_OUTPUT.PUT(Emp_row.Ename || ' ');
DBMS_OUTPUT.PUT_LINE(Emp_row.Sal);
END LOOP;
END;

Implementing Variant Records

The power of cursor variables comes from their ability to point to different cursors. In the following package example, a discriminant is used to open a cursor variable to point to one of two different cursors:

CREATE OR REPLACE PACKAGE Emp_dept_data AS
TYPE Cv_type IS REF CURSOR;
PROCEDURE Open_cv (Cv IN OUT cv_type,
Discrim IN POSITIVE);
END Emp_dept_data;

CREATE OR REPLACE PACKAGE BODY Emp_dept_data AS
PROCEDURE Open_cv (Cv IN OUT cv_type,
Discrim IN POSITIVE) IS
BEGIN
IF Discrim = 1 THEN
OPEN Cv FOR SELECT * FROM Emp_tab WHERE Sal > 2000;
ELSIF Discrim = 2 THEN
OPEN Cv FOR SELECT * FROM Dept_tab;
END IF;
END Open_cv;
END Emp_dept_data;


You can call the Open_cv procedure to open the cursor variable and point it to either a query on the Emp_tab table or the Dept_tab table. The following PL/SQL block shows how to fetch using the cursor variable, and then use the ROWTYPE_MISMATCH predefined exception to handle either fetch:

DECLARE
Emp_rec Emp_tab%ROWTYPE;
Dept_rec Dept_tab%ROWTYPE;
Cv Emp_dept_data.CV_TYPE;

BEGIN
Emp_dept_data.open_cv(Cv, 1); -- Open Cv For Emp_tab Fetch
Fetch cv INTO Dept_rec; -- but fetch into Dept_tab record
-- which raises ROWTYPE_MISMATCH
DBMS_OUTPUT.PUT(Dept_rec.Deptno);
DBMS_OUTPUT.PUT_LINE(' ' || Dept_rec.Loc);

EXCEPTION
WHEN ROWTYPE_MISMATCH THEN
BEGIN
DBMS_OUTPUT.PUT_LINE
('Row type mismatch, fetching Emp_tab data...');
FETCH Cv INTO Emp_rec;
DBMS_OUTPUT.PUT(Emp_rec.Deptno);
DBMS_OUTPUT.PUT_LINE(' ' || Emp_rec.Ename);
END;