COUNT

The COUNT function returns the number of rows or values in a set of rows or values.

expression: The argument values can be of any built-in data type other than a DataLink. XML is not allowed for COUNT (DISTINCT expression).

The result of the function is a large integer and it must be within the range of large integers. The result cannot be null. If the table is a distributed table, then the result is DECIMAL(15,0). For more information about distributed tables, see the DB2® Multisystem topic collection.

The argument of COUNT(*) is a set of rows. The result is the number of rows in the set. A row that includes only null values is included in the count.

The argument of COUNT(expression) or COUNT(ALL expression) is a set of values. The function is applied to the set derived from the argument values by the elimination of null values. The result is the number of non-null values in the set including duplicates.

The argument of COUNT(DISTINCT expression) is a set of values. The function is applied to the set of values derived from the argument values by the elimination of null values and duplicate values. The result is the number of values in the set.

If a collating sequence other than *HEX is in effect when the statement that contains the COUNT(DISTINCT expression) is executed and the arguments are SBCS data, mixed data, or Unicode data, then the result is obtained by comparing weighted values for each value in the set. The weighted values are based on the collating sequence.

Examples

Using the EMPLOYEE table, set the host variable FEMALE (INTEGER) to the number of rows where the value of the SEX column is ‘F'.
```
   SELECT COUNT(*)
     INTO :FEMALE
     FROM EMPLOYEE
     WHERE SEX = 'F'
```
Results in FEMALE being set to 19.
Using the EMPLOYEE table, set the host variable FEMALE_IN_DEPT (INTEGER) to the number of departments (WORKDEPT) that have at least one female as a member.
```
     SELECT COUNT(DISTINCT WORKDEPT)
       INTO :FEMALE_IN_DEPT
       FROM EMPLOYEE
       WHERE SEX='F'
```
Results in FEMALE_IN_DEPT being set to 6. (There is at least one female in departments A00, C01, D11, D21, E11, and E21.)