DBPARTITIONNUM scalar function

The schema is SYSIBM.

column-name

The qualified or unqualified name of any column in the table. Because row-level information is returned, the result is the same regardless of which column is specified. The column can have any data type.

If column-name references a column in a view, the expression for the column in the view must reference a column of the underlying base table, and the view must be deletable. A nested or common table expression follows the same rules as a view.

The specific row (and table) for which the database partition number is returned by the DBPARTITIONNUM function is determined from the context of the SQL statement that uses the function.

The database partition number returned on transition variables and tables is derived from the current transition values of the distribution key columns. For example, in a before insert trigger, the function returns the projected database partition number, given the current values of the new transition variables. However, the values of the distribution key columns might be modified by a subsequent before insert trigger. Thus, the final database partition number of the row when it is inserted into the database might differ from the projected value.

The data type of the result is INTEGER and is never null. If there is no db2nodes.cfg file, the result is 0.

Notes

• The DBPARTITIONNUM function cannot be used on replicated tables, within check constraints, or in the definition of generated columns (SQLSTATE 42881).
• The DBPARTITIONNUM function cannot be used as a source function when creating a user-defined function. Because it accepts any data type as an argument, it is not necessary to create additional signatures to support user-defined distinct types.
• Syntax alternatives: For compatibility with previous versions of DB2® products, the function name NODENUMBER is a synonym for DBPARTITIONNUM.

Examples

• Example 1: Count the number of instances in which the row for a given employee in the EMPLOYEE table is on a different database partition than the description of the employee's department in the DEPARTMENT table.

     SELECT COUNT(*) FROM DEPARTMENT D, EMPLOYEE E
       WHERE D.DEPTNO=E.WORKDEPT
       AND DBPARTITIONNUM(E.LASTNAME) <> DBPARTITIONNUM(D.DEPTNO)

• Example 2: Join the EMPLOYEE and DEPARTMENT tables so that the rows of the two tables are on the same database partition.

     SELECT * FROM DEPARTMENT D, EMPLOYEE E
       WHERE DBPARTITIONNUM(E.LASTNAME) = DBPARTITIONNUM(D.DEPTNO)

• Example 3: Using a before trigger on the EMPLOYEE table, log the employee number and the projected database partition number of any new row in the EMPLOYEE table in a table named EMPINSERTLOG1.

     CREATE TRIGGER EMPINSLOGTRIG1
     BEFORE INSERT ON EMPLOYEE
     REFERENCING NEW AW NEWTABLE
     FOR EACH ROW
     INSERT INTO EMPINSERTLOG1
     VALUES(NEWTABLE.EMPNO, DBPARTITIONNUM
     (NEWTABLE.EMPNO))