Returns the number of items in a group. COUNT_BIG works like the COUNT function. The only difference between the two functions is their return values. COUNT_BIG always returns a bigint data type value. COUNT always returns an int data type value. May be followed by the OVER Clause (Transact-SQL).
Applies the aggregate function to all values. ALL is the default.
Specifies that COUNT_BIG returns the number of unique nonnull values.
Is an expression of any type. Aggregate functions and subqueries are not permitted.
Specifies that all rows should be counted to return the total number of rows in a table. COUNT_BIG(*) takes no parameters and cannot be used with DISTINCT. COUNT_BIG(*) does not require an expression parameter because, by definition, it does not use information about any particular column. COUNT_BIG(*) returns the number of rows in a specified table without getting rid of duplicates. It counts each row separately. This includes rows that contain null values.