Skip Headers
Oracle® Database SQL Language Reference
11g Release 1 (11.1)

B28286-07
Go to Documentation Home
Home
Go to Book List
Book List
Go to Table of Contents
Contents
Go to Index
Index
Go to Master Index
Master Index
Go to Feedback page
Contact Us

Go to previous page
Previous
Go to next page
Next
PDF · Mobi · ePub

CURSOR Expressions

A CURSOR expression returns a nested cursor. This form of expression is equivalent to the PL/SQL REF CURSOR and can be passed as a REF CURSOR argument to a function.

Description of cursor_expression.gif follows
Description of the illustration cursor_expression.gif

A nested cursor is implicitly opened when the cursor expression is evaluated. For example, if the cursor expression appears in a select list, a nested cursor will be opened for each row fetched by the query. The nested cursor is closed only when:

Restrictions on CURSOR Expressions The following restrictions apply to CURSOR expressions:

Examples  The following example shows the use of a CURSOR expression in the select list of a query:

SELECT department_name, CURSOR(SELECT salary, commission_pct 
   FROM employees e
   WHERE e.department_id = d.department_id)
   FROM departments d
   ORDER BY department_name;

The next example shows the use of a CURSOR expression as a function argument. The example begins by creating a function in the sample OE schema that can accept the REF CURSOR argument. (The PL/SQL function body is shown in italics.)

CREATE FUNCTION f(cur SYS_REFCURSOR, mgr_hiredate DATE) 
   RETURN NUMBER IS
   emp_hiredate DATE;
   before number :=0;
   after number:=0;
begin
  loop
    fetch cur into emp_hiredate;
    exit when cur%NOTFOUND;
    if emp_hiredate > mgr_hiredate then
      after:=after+1;
    else
      before:=before+1;
    end if;
  end loop;
  close cur;
  if before > after then
    return 1;
  else
    return 0;
  end if;
end;
/

The function accepts a cursor and a date. The function expects the cursor to be a query returning a set of dates. The following query uses the function to find those managers in the sample employees table, most of whose employees were hired before the manager.

SELECT e1.last_name FROM employees e1
   WHERE f(
   CURSOR(SELECT e2.hire_date FROM employees e2
   WHERE e1.employee_id = e2.manager_id),
   e1.hire_date) = 1
   ORDER BY last_name;
 
LAST_NAME
-------------------------
Cambrault
De Haan
Higgins
Mourgos
Zlotkey