1. A method comprising: receiving a plurality of search key word sets that were previously input by a plurality of users; obtaining category information corresponding to the plurality of search key word sets, the category information being determined based on at least in part on the plurality of users' selections; segmenting each of the plurality of search key word sets into search key word units; combining the search key word units into a plurality of search key word unit groups that correspond to a plurality of stages, the search key word unit groups corresponding to the same stage having the same number of search key word units; based at least in part on the category information corresponding to the plurality of search key word sets, determining category information that specifically corresponds to the plurality of search key word unit groups; and based at least in part on category information specifically corresponding to the plurality of search key word unit groups, establishing a plurality of search key word tables corresponding to the plurality of stages, each stage having a corresponding search key word table that comprises the correspondence between the search key word unit groups for said each stage and the category information that specificallys correspond to the plurality of search key word unit groups; wherein: the plurality of search key word tables are used to provide current category information of a current search key word set input by a user.