Techniques are disclosed relating to creating an index for a database system. In one embodiment, a database system stores data within a plurality of fields in a data table, a subset of the data being associated with a particular one of the plurality of fields. The database system receives a request to index the data table based on the particular field and analyzes the subset of the data. In response to determining, based on the analyzing, that one or more duplicate values are present in the subset of data, the database system sets, in an index table having the particular field, an indication identifying which entries of the index table have a duplicate value for the particular field, and returns a response to the request that specifies the one or more duplicate values. In some embodiments, the response includes a user interface displaying one or more duplicates values.