SQL COUNT() 函数

  +-----+---------+-------+------------+

  | aid | site_id | count | date |

  +-----+---------+-------+------------+

  | 1 | 1 | 45 | 2016-05-10 |

  | 2 | 3 | 100 | 2016-05-13 |

  | 3 | 1 | 230 | 2016-05-14 |

  | 4 | 2 | 10 | 2016-05-14 |

  | 5 | 5 | 205 | 2016-05-14 |

  | 6 | 4 | 13 | 2016-05-15 |

  | 7 | 3 | 220 | 2016-05-15 |

  | 8 | 5 | 545 | 2016-05-16 |

  | 9 | 3 | 201 | 2016-05-17 |

  +-----+---------+-------+------------+