4.9.1.2 COUNT

Syntax

COUNT ( { [ALL] expression } | { DISTINCT column_ref } | * )

Description

The aggregate function COUNT computes either the number of rows in a group of rows or the number of non-null values in a group of values.

• The keyword DISTINCT specifies that the duplicate values are to be eliminated before computing the count.
• If the argument to COUNT function is '*', then the function computes the count of the number of rows in group.
• If the argument to COUNT function is not '*', then null values are eliminated before the number of rows is computed.
• The argument column_ref or expression can be of any type.
• The result of the function is of INTEGER type. The result is never null.

Example

SELECT COUNT (*)
    FROM orders
    WHERE order_date = SYSDATE ;