COUNT

Syntax

See Also:

Analytic Functions for information on syntax, semantics, and restrictions

Purpose

COUNT returns the number of rows returned by the query. You can use it as an aggregate or analytic function.

If you specify DISTINCT, then you can specify only the query_partition_clause of the analytic_clause. The order_by_clause and windowing_clause are not allowed.

If you specify expr, then COUNT returns the number of rows where expr is not null. You can count either all rows, or only distinct values of expr.

If you specify the asterisk (*), then this function returns all rows, including duplicates and nulls. COUNT never returns null.

Note:

Before performing a COUNT (DISTINCT expr)operation on a large amount of data, consider using one of the following methods to obtain approximate results more quickly than exact results:

  • Set the APPROX_FOR_COUNT_DISTINCT initialization parameter to true before using the COUNT (DISTINCT expr) function. Refer to Oracle Database Reference for more information on this parameter.

  • Use the APPROX_COUNT_DISTINCT function instead of the COUNT (DISTINCT expr) function. Refer to APPROX_COUNT_DISTINCT.

See Also:

Aggregate Examples

The following examples use COUNT as an aggregate function:

SELECT COUNT(*) "Total"
  FROM employees;

     Total
----------
       107

SELECT COUNT(*) "Allstars"
  FROM employees
  WHERE commission_pct > 0;

 Allstars
---------
       35

SELECT COUNT(commission_pct) "Count"
  FROM employees;

     Count
----------
        35

SELECT COUNT(DISTINCT manager_id) "Managers"
  FROM employees;

  Managers
----------
        18

Analytic Example

The following example calculates, for each employee in the employees table, the moving count of employees earning salaries in the range 50 less than through 150 greater than the employee's salary.

SELECT last_name, salary,
       COUNT(*) OVER (ORDER BY salary RANGE BETWEEN 50 PRECEDING AND
                      150 FOLLOWING) AS mov_count
  FROM employees
  ORDER BY salary, last_name;

LAST_NAME                     SALARY  MOV_COUNT
------------------------- ---------- ----------
Olson                           2100          3
Markle                          2200          2
Philtanker                      2200          2
Gee                             2400          8
Landry                          2400          8
Colmenares                      2500         10
Marlow                          2500         10
Patel                           2500         10
. . .