Given: table of the form

field1 | field2 | fieldN |

a | a | ... |

a | b | ... |

b | a | ... |

a | b | ... |

a | a | ... |

b | b | ... |

Please tell me how to get a unique combination of two fields and the number of such combinations.Those.the result should be like this

field1 | field2 | count |

a | a | 2 |

a | b | 2 |

b | a | 1 |

b | b | 1 |

Thank.