This paper presents an approach aimed at mining a new type of pattern in data, namely analogical proportions. An analogical proportion expresses the equality of the relationships between the attributes of two pairs of structured objects. This notion is investigated in the database context for the discovery of different forms of "parallels" between tuples. First, we give a formal definition of the analogical proportion in the setting of relational databases. Then we focus on the problem of mining analogical proportions. We show that it is possible to use a clustering approach for building equivalence classes made of pairs of tuples that are bound by the same relationship of analogical proportion. This work can be seen as a first step to the extension of database query languages that could be completed with "analogical queries".