See Also:"Analytic Functions" for information on syntax, semantics, and restrictions, including valid forms of
LEAD is an analytic function. It provides access to more than one row of a table at the same time without a self join. Given a series of rows returned from a query and a position of the cursor,
LEAD provides access to a row at a given physical offset beyond that position.
If you do not specify
offset, then its default is 1. The optional
default value is returned if the offset goes beyond the scope of the table. If you do not specify
default, then its default value is null.
You cannot use
LEAD or any other analytic function for
value_expr. That is, you cannot nest analytic functions, but you can use other built-in function expressions for
The following example provides, for each employee in the
employees table, the hire date of the employee hired just after:
SELECT last_name, hire_date, LEAD(hire_date, 1) OVER (ORDER BY hire_date) AS "NextHired" FROM employees WHERE department_id = 30; LAST_NAME HIRE_DATE NextHired ------------------------- --------- --------- Raphaely 07-DEC-94 18-MAY-95 Khoo 18-MAY-95 24-JUL-97 Tobias 24-JUL-97 24-DEC-97 Baida 24-DEC-97 15-NOV-98 Himuro 15-NOV-98 10-AUG-99 Colmenares 10-AUG-99