debrah.h48 Said..
You must select tables for a SELECT, UPDATE, or DELETE statement before you can add a search condition in the WHERE or HAVING clause.
For a SELECT statement, you should select grouping columns before you add a search condition in the HAVING clause.
A search condition specifies a condition that is true, false, or unknown about a given row (WHERE clause) or group (HAVING clause). The result of a search condition is derived by application of the specified logical operators (AND, OR, NOT) to the result of each specified predicate. If logical operators are not specified, the result of the search condition is the result of the specified individual predicate.
Get more information here: http://publib.boulder.ibm.com/infocenter/db2luw/v8/index.jsp?topic=/com.ibm.db2.udb.sqlassist2.doc/sqlassist2/t_condbuild.htm