A compound statement consists of two or more simple statements that have been connected by the Boolean operators "AND" or "OR". The completed statement must have matching opening and closing parenthesis characters.
The Boolean "AND" or "OR" operators may be placed inside a set of matching parenthesis. For example - "(SUBJECT CONTAINS "TEST" OR SUBJECT CONTAINS "PLAN")" will find any message with the words "test" or "plan" in the subject.
The Boolean operators may also be placed between simple statements. For example: "(AUTHOR CONTAINS "JOE") AND (AUTHOR CONTAINS "BOB")" will find any document that was written by someone with the name "Joe" or "Bob".
The operators may appear in both places, as outlined in sections a) and b) (above). An illustration is better than a 1000 words here: "(APPOINTMENT AND START_DATE = TODAY) OR (NOTE AND START_DATE = TODAY) OR (TASK AND START_DATE = TODAY)" will find any Appointment, Reminder Note, or Task that belongs to the current day.