Oracle PL/SQL Tutorial/Cursor/refcursor

Reference cursor type

SQL>
SQL> create table t ( x varchar2(5) );
Table created.
SQL>
SQL> declare
  2      type rc is ref cursor;
  3      l_cursor rc;
  4  begin
  5      for i in 1 .. 5000
  6      loop
  7          open l_cursor for "select x from t where x = " || to_char(i);
  8          close l_cursor;
  9      end loop;
 10  end;
 11  /
PL/SQL procedure successfully completed.
SQL>
SQL> declare
  2      type rc is ref cursor;
  3      l_cursor rc;
  4  begin
  5      for i in 1 .. 5000
  6      loop
  7          open l_cursor for "select x from t where x = :x" using i;
  8          close l_cursor;
  9      end loop;
 10  end;
 11  /
PL/SQL procedure successfully completed.
SQL>
SQL> drop table t;
Table dropped.
SQL>
SQL>

reference cursor variable

SQL>
SQL>
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> variable a refcursor
SQL> variable b refcursor
SQL> variable c refcursor
SQL> alter session set sql_trace=true;
Session altered.
SQL> begin
  2      open :a for select empno from emp q1 where ename = "BLAKE";
  3      open :b for select empno from emp q2 where ename = "BLAKE";
  4      open :c for select empno from emp q3 where ename = "SMITH";
  5  end;
  6  /
PL/SQL procedure successfully completed.
SQL> print a
     EMPNO
----------
      7698
SQL> begin
  2      for i in 1 .. 1000
  3      loop
  4          update emp set sal = sal where ename = "BLAKE";
  5          commit;
  6      end loop;
  7      delete from emp
  8       where ename = "SMITH";
  9      commit;
 10  end;
 11  /
PL/SQL procedure successfully completed.
SQL> print b
     EMPNO
----------
      7698
SQL> print c
     EMPNO
----------
      7369
SQL>
SQL> alter session set sql_trace=false;
Session altered.
SQL> drop table emp;
Table dropped.
SQL>

return sys_refcursor from a function

SQL> CREATE TABLE EMP(
  2      EMPNO NUMBER(4) NOT NULL,
  3      ENAME VARCHAR2(10),
  4      JOB VARCHAR2(9),
  5      MGR NUMBER(4),
  6      HIREDATE DATE,
  7      SAL NUMBER(7, 2),
  8      COMM NUMBER(7, 2),
  9      DEPTNO NUMBER(2)
 10  );
Table created.
SQL> INSERT INTO EMP VALUES(2, "Jack", "Tester", 6,TO_DATE("20-FEB-1981", "DD-MON-YYYY"), 1600, 300, 30);
1 row created.
SQL> INSERT INTO EMP VALUES(3, "Wil", "Tester", 6,TO_DATE("22-FEB-1981", "DD-MON-YYYY"), 1250, 500, 30);
1 row created.
SQL> INSERT INTO EMP VALUES(4, "Jane", "Designer", 9,TO_DATE("2-APR-1981", "DD-MON-YYYY"), 2975, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES(5, "Mary", "Tester", 6,TO_DATE("28-SEP-1981", "DD-MON-YYYY"), 1250, 1400, 30);
1 row created.
SQL> INSERT INTO EMP VALUES(7, "Chris", "Designer", 9,TO_DATE("9-JUN-1981", "DD-MON-YYYY"), 2450, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES(8, "Smart", "Helper", 4,TO_DATE("09-DEC-1982", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES(9, "Peter", "Manager", NULL,TO_DATE("17-NOV-1981", "DD-MON-YYYY"), 5000, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES(10, "Take", "Tester", 6,TO_DATE("8-SEP-1981", "DD-MON-YYYY"), 1500, 0, 30);
1 row created.
SQL> INSERT INTO EMP VALUES(13, "Fake", "Helper", 4,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL>
SQL> create or replace function emp_list return sys_refcursor is
  2   rc sys_refcursor;
  3   begin
  4   open rc for select * from emp;
  5   return rc;
  6   end;
  7  /
Function created.
SQL>
SQL> create or replace procedure list_emps is
  2   e sys_refcursor;
  3   r emp%rowtype;
  4  begin
  5   e := emp_list;
  6   loop
  7       fetch e into r;
  8       exit when e%notfound;
  9       dbms_output.put_line(r.empno||","||r.hiredate);
 10   end loop;
 11   close e;
 12   end;
 13  /
Procedure created.
SQL>
SQL> drop table emp;
Table dropped.