COUNT function [Aggregate]

COUNT( [ * | [ ALL | DISTINCT ] expression ] )

COUNT( [ * | [ ALL ]expression ] ) OVER ( window-spec )

window-spec : see Syntax 2 instructions in the Remarks section below

* Return the number of rows in each group. COUNT(*) and COUNT() are semantically equivalent.
[ ALL ] expression Return the number of rows in each group where the value of expression is not NULL.
DISTINCT expression Return the number of distinct values of expression for all of the rows in each group where expression is not NULL.

The COUNT function returns a value of type INT.

COUNT never returns the value NULL. If a group contains no rows, or if there are no non-NULL values of expression in a group, then COUNT returns 0.

The COUNT function returns a maximum value of 2147483647. Use the COUNT_BIG function when counting large result sets, the result might have more rows, or there is a possibility of overflow.

Syntax 2 represents usage as a window function in a SELECT statement. As such, elements of window-spec can be specified either in the function syntax (inline), or in conjunction with a WINDOW clause in the SELECT statement. See the window-spec definition in WINDOW clause.

For more information about using window functions in SELECT statements, including working examples, see Window functions.

For more information about specifying a window specification in an OVER clause, see Window definition: Inlining using the OVER clause and WINDOW clause.

SQL/2008 Core feature. When used as a window function (Syntax 2), COUNT comprises part of optional SQL/2008 language feature T611, "Basic OLAP operations".
The ability to specify DISTINCT over an expression that is not a column reference comprises part of optional SQL language feature F561, "Full value expressions". SQL Anywhere also supports SQL/2008 language feature F441, "Extended set function support", which permits operands of aggregate functions to be arbitrary expressions possibly including outer references to expressions in other query blocks that are not column references.

SQL Anywhere does not support optional SQL/2008 feature F442, "Mixed column references in set functions". SQL Anywhere does not permit the arguments of an aggregate function to include both a column reference from the query block containing the COUNT function, combined with an outer reference.

For an example, see AVG function [Aggregate].

Aggregate functions and outer references

The following statement returns each unique city, and the number of employees working in that city.

SELECT City, COUNT( * ) FROM Employees GROUP BY City;

COUNT function [Aggregate]

Syntax 1

Syntax 2

Parameters

Returns

Remarks

See also

Standards and compatibility

See also

Example