In this article we present how to implement fuzzy databases based on the relational model. This approach includes many fuzzy attribute types, which can express the most of fuzzy knowledge types. These fuzzy attribute types include imprecise attributes, fuzzy attributes associated to one or more attributes or with an independent meaning. In order to represent such fuzzy information we must study two aspects of fuzzy information: how to represent fuzzy data and how to represent fuzzy metaknowledge data. This second information is very important and it must be considered in any fuzzy database. This article studies the fuzzy metaknowledge data for any fuzzy attribute and how to represent both in a relational database.