1. A method for constructing a query hierarchy, the method comprising: receiving a first query; generating a candidate query list comprising one or more candidate queries, wherein the one or more candidate queries are determined based upon a relative coverage determined between the first query and each candidate query, the relative coverage between the first query and a candidate query representing a similarity between the content of pages clicked by a user in response to the candidate query and the content of pages clicked by a user in response to the first query determined from click-through data; determining hierarchical relationships between the first query relative and each of the one or more candidate queries comprising the candidate query list, wherein each of the hierarchical relationships comprises one of a parent relationship, a child relationship, or a sibling relationship; and constructing a query hierarchy based on the hierarchical relationships between the first query and each of the one or more candidate queries comprising the candidate query list.