A disappearing index allows faster processing of a database query without the startup time of a prior art sparse index. The disappearing index starts as a full index but is trimmed of index values that point to a row in the table that is not selected by the query. Thus the traditional index disappears as it becomes a sparse index tailored to the query. The query is able to execute faster using the now sparse index since the target database table is not accessed for duplicate values in the base table of the query. The query optimizer may determine to use a disappearing index based on estimates of the number of duplicate values in the base table. When the query is complete, the created disappearing table may be discarded or used for other queries that match the selection of the query that created the disappearing index.