Editing Relational model (section)

=== Algorithm to derive candidate keys from functional dependencies ===
 '''algorithm''' derive candidate keys from functional dependencies '''is'''
     '''input:''' a set ''S'' of FDs that contain only subsets of a header ''H''
     '''output:''' the set ''C'' of superkeys that hold as candidate keys in
             all relation universes over ''H'' in which all FDs in ''S'' hold
 
     ''C'' := ∅         // found candidate keys
     ''Q'' := { ''H'' }      // superkeys that contain candidate keys
     '''while''' ''Q'' <> ∅ '''do'''
         let ''K'' be some element from ''Q''
         ''Q'' := ''Q''&nbsp;– { ''K'' }
         ''minimal'' := '''true'''
         '''for each''' ''X->Y'' '''in''' ''S'' '''do'''
             ''K' '':= (''K''&nbsp;– ''Y'') ∪ ''X''   // derive new superkey
             '''if''' ''K' ''⊂ ''K'' '''then'''
                 ''minimal'' := '''false'''
                 ''Q'' := ''Q'' ∪ { ''K' ''}
             '''end if'''
         '''end for'''
         '''if''' ''minimal'' '''and''' there is not a subset of ''K'' in ''C'' '''then'''
             remove all supersets of ''K'' from ''C''
             ''C'' := ''C'' ∪ { ''K'' }
         '''end if'''
     '''end while'''