Abstract: In a computerized database system, a query is formulated to retrieve data from the database by interactively identifying at least one table containing query data, and at least one column and at least one row in the identified table containing the query data. The rows are interactively identified using a condition statement. The condition statement is interactively formulated using at least one displayed flowline. Input is received from the user specifying a position on the flowline for insertion of a predicate and the predicate. The flowline is displayed with the predicate inserted in the specified location. The predicates are displayed on the flowline in between nodes. Predicates on the same flowline are combined through a logical AND operation. Predicates on different flowlines between the same nodes are combined through a logical OR operation. The flowline is converted to a corresponding Boolean algebra statement and displayed.