1. A computer-implemented method for a user to build a query to a database, the method comprising the steps of: displaying to the user in a first window a graphical representation of a plurality of user-selectable icons corresponding to a plurality of columns defined in the database, wherein the graphical representation includes a plurality of domains, each domain of the plurality of domains defines a logical grouping of columns in the database, the graphical representation including at least one line connecting the plurality of user-selectable icons to represent at least one relationship in the database; in response to user selection of an icon in the graphical representation corresponding to a first column in a first step in building the query, altering the graphical representation to make at least one icon corresponding to at least one different column in the graphical representation unavailable for selection by the user in a subsequent step in building the query according to at least one predefined rule for the first column that specifies at least one restriction between the fist column and the at least one different column, wherein the at least one predefined rule includes at least one condition for displaying said each domain of the plurality of domains, wherein the at least one restriction comprises mutual exclusion for the first column and the at least one different column and the at least one restriction specifies a reciprocal keyword that causes automatic generation of reciprocal restrictions between the first column and the at least one different column, wherein the altering the graphical representation to make the at least one icon corresponding to at least one column in the graphical representation unavailable for selection by the user comprises at least one of the following steps: eliminating the at least one icon corresponding to the at least one different column from the graphical representation; hiding the at least one icon corresponding to the at least one different column in the graphical representation from view of the user; and greying out the at least one icon corresponding to the at least one different column in the graphical representation; during display of the graphical representation in the first window, displaying in a second window at least one selectable value corresponding to values in the database corresponding to the first column; and resetting the at least one restriction to make the at least one different column in the graphical representation available for selection by the user when the user specifies an OR operator when building the query.