Oracle: Howto use Cursors and Dynamic Cursors

1. Open cursor with a dynamic select statement

SQL>
SQL> CREATE TABLE EMP (EMPNO NUMBER(4) NOT NULL,
2 ENAME VARCHAR2(10),
3 JOB VARCHAR2(9),
4 MGR NUMBER(4),
5 HIREDATE DATE,
6 SAL NUMBER(7, 2),
7 COMM NUMBER(7, 2),
8 DEPTNO NUMBER(2));
Table created.
SQL>
SQL> INSERT INTO EMP VALUES (7369, 'SMITH', 'CLERK', 7902, TO_DATE('17-DEC-1980', 'DD-MON-YYYY'), 800, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7499, 'ALLEN', 'SALESMAN', 7698, TO_DATE('20-FEB-1981', 'DD-MON-YYYY'), 1600, 300, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7521, 'WARD', 'SALESMAN', 7698, TO_DATE('22-FEB-1981', 'DD-MON-YYYY'), 1250, 500, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7566, 'JONES', 'MANAGER', 7839, TO_DATE('2-APR-1981', 'DD-MON-YYYY'), 2975, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7654, 'MARTIN', 'SALESMAN', 7698,TO_DATE('28-SEP-1981', 'DD-MON-YYYY'), 1250, 1400, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7698, 'BLAKE', 'MANAGER', 7839,TO_DATE('1-MAY-1981', 'DD-MON-YYYY'), 2850, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7782, 'CLARK', 'MANAGER', 7839,TO_DATE('9-JUN-1981', 'DD-MON-YYYY'), 2450, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES (7788, 'SCOTT', 'ANALYST', 7566,TO_DATE('09-DEC-1982', 'DD-MON-YYYY'), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7839, 'KING', 'PRESIDENT', NULL,TO_DATE('17-NOV-1981', 'DD-MON-YYYY'), 5000, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES (7844, 'TURNER', 'SALESMAN', 7698,TO_DATE('8-SEP-1981', 'DD-MON-YYYY'), 1500, 0, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7876, 'ADAMS', 'CLERK', 7788,TO_DATE('12-JAN-1983', 'DD-MON-YYYY'), 1100, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7900, 'JAMES', 'CLERK', 7698,TO_DATE('3-DEC-1981', 'DD-MON-YYYY'), 950, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7902, 'FORD', 'ANALYST', 7566,TO_DATE('3-DEC-1981', 'DD-MON-YYYY'), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7934, 'MILLER', 'CLERK', 7782,TO_DATE('23-JAN-1982', 'DD-MON-YYYY'), 1300, NULL, 10);
1 row created.
SQL>
SQL>
SQL> CREATE OR REPLACE PROCEDURE showemps (where_in IN VARCHAR2 := NULL)
2 IS
3 TYPE cv_typ IS REF CURSOR;
4 cv cv_typ;
5 v_nm emp.ename%TYPE;
6 BEGIN
7 OPEN cv FOR
8 'SELECT ename FROM emp WHERE ' || NVL (where_in, '1=1');
9 LOOP
10 FETCH cv INTO v_nm;
11 EXIT WHEN cv%NOTFOUND;
12 DBMS_OUTPUT.PUT_LINE (v_nm);
13 END LOOP;
14 CLOSE cv;
15 END;
16 /
Procedure created.
SQL>
SQL> show error
No errors.
SQL>
SQL> EXEC showemps(null);
SMITH
ALLEN
WARD
JONES
MARTIN
BLAKE
CLARK
SCOTT
KING
TURNER
ADAMS
JAMES
FORD
MILLER
PL/SQL procedure successfully completed.
SQL>
SQL>
SQL> drop table emp;
Table dropped.

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2. Opening multiple queries using the same cursor variable

SQL> create table product(
2 product_id number(4) not null,
3 product_description varchar2(20) not null
4 );
Table created.
SQL>
SQL> insert into product values (1,'Java');
1 row created.
SQL> insert into product values (2,'Oracle');
1 row created.
SQL> insert into product values (3,'C#');
1 row created.
SQL> insert into product values (4,'Javascript');
1 row created.
SQL> insert into product values (5,'Python');
1 row created.
SQL>
SQL>
SQL> create table company(
2 product_id number(4) not null,
3 company_id NUMBER(8) not null,
4 company_short_name varchar2(30) not null,
5 company_long_name varchar2(60)
6 );
Table created.
SQL> insert into company values(1,1001,'A Inc.','Long Name A Inc.');
1 row created.
SQL> insert into company values(1,1002,'B Inc.','Long Name B Inc.');
1 row created.
SQL> insert into company values(1,1003,'C Inc.','Long Name C Inc.');
1 row created.
SQL> insert into company values(2,1004,'D Inc.','Long Name D Inc.');
1 row created.
SQL> insert into company values(2,1005,'E Inc.','Long Name E Inc.');
1 row created.
SQL> insert into company values(2,1006,'F Inc.','Long Name F Inc.');
1 row created.
SQL>
SQL> DECLARE
2 TYPE rc is REF CURSOR;
3 refCursorValue rc;
4 productRecord product%ROWTYPE;
5 v_product_description VARCHAR2(20);
6 v_company_short_name VARCHAR2(30);
7 BEGIN
8 OPEN refCursorValue FOR SELECT *from product;
9
10 LOOP
11 FETCH refCursorValue INTO productRecord;
12 EXIT WHEN refCursorValue%NOTFOUND;
13 dbms_output.put_line(to_char(productRecord.product_id)||' '||
14 rpad(productRecord.product_description,20,' '));
15 END LOOP;
16
17 OPEN refCursorValue FOR SELECT h.product_description,o.company_short_name
18 FROM company o,product h
19 WHERE o.product_id =h.product_id;
20
21 LOOP
22 FETCH refCursorValue INTO v_product_description,v_company_short_name;
23 EXIT WHEN refCursorValue%NOTFOUND;
24 dbms_output.put_line(rpad(v_product_description,20,' ')||' '||rpad(v_company_short_name,30,' '));
25 END LOOP;
26 CLOSE refCursorValue;
27 END;
28 /
1 Java
2 Oracle
3 C#
4 Javascript
5 Python
Java A Inc.
Java B Inc.
Java C Inc.
Oracle D Inc.
Oracle E Inc.
Oracle F Inc.
PL/SQL procedure successfully completed.
SQL>
SQL>
SQL> drop table product;
Table dropped.
SQL> drop table company;
Table dropped.

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3.Dyamic cursors in PL/SQL

create or replace package dynamic_cursor is

  type t_crs is ref cursor;

  procedure dyn_sel (
       tab_name   in varchar2,
       field_name in varchar2,
       val        in varchar2,
       crs        in out t_crs);

  procedure openCursor;

end dynamic_cursor;             
/

create or replace package body dynamic_cursor as
   procedure dyn_sel (
          tab_name   in varchar2,
          field_name in varchar2,
          val        in varchar2,
          crs        in out t_crs)

   is
     stmt varchar2(100);
   begin
     stmt := 'select * from ' || tab_name || ' where ' || field_name || ' = :1 ';

     open crs for stmt using val;
   end dyn_sel;

   procedure openCursor is
     tc t_crs;
     f1 varchar2(50);
     f2 varchar2(50);
   begin
     dyn_sel('test_for_cursor','a','two',tc);
     loop
       fetch tc into f1,f2;
       exit when tc%notfound;
       dbms_output.put_line(f2);
     end loop;
   end openCursor;
     
end dynamic_cursor;     
/

begin
  dynamic_cursor.openCursor;
end;
/