The State of the UNION
by Skip Marchesani

DB2 for i supports the concept of union, which creates or derives a single result set table by combining two other result set tables, each of which was derived from a SELECT statement or another UNION. (See the discussion on cascading unions at the end of this article). A union is very useful when an SQL query must operate on two or more tables where JOIN cannot be used to produce the desired result set table. READ MORE >

A Good Use for Global Variables
by Ted Holt

Using global data (fields, variables and constants) is generally considered to be poor programming practice. One reason is that a subroutine or subprocedure that uses global data is not easily placed into service elsewhere. Another reason is that undesirable side effects may occur when one routine changes a variable that another routine uses. However, in some situations global data makes sense. I would like to provide one example. READ MORE >