This topic describes the aggregate functions. Some functions are not supported by PolarDB-X 1.0.

## Supported functions

The following table describes the aggregate functions that are supported by PolarDB-X 1.0.

Function | Description |
---|---|

AVG() | Return the average value of the argument |

COUNT() | Return a count of the number of rows returned |

COUNT(DISTINCT) | Return the count of a number of different values |

MAX() | Return the maximum value |

MIN() | Return the minimum value |

SUM() | Return the sum |

## Unsupported functions

The following table describes the aggregate functions that are not supported by PolarDB-X 1.0. These functions are supported by databases that run on the MySQL 5.7 engine.

Function | Description |
---|---|

BIT_AND() | Return bitwise AND |

BIT_OR() | Return bitwise OR |

BIT_XOR() | Return bitwise XOR |

GROUP_CONCAT() | Return a concatenated string |

STD() | Return the population standard deviation |

STDDEV() | Return the population standard deviation |

STDDEV_POP() | Return the population standard deviation |

STDDEV_SAMP() | Return the sample standard deviation |

VAR_POP() | Return the population standard variance |

VAR_SAMP() | Return the sample variance |

VARIANCE() | Return the population standard variance |