| # Aggregate Functions |
| |
| HoraeDB SQL is implemented with [DataFusion](https://github.com/apache/arrow-datafusion), Here is the list of aggregate functions. See more detail, Refer to [Datafusion](https://github.com/apache/arrow-datafusion/blob/master/docs/source/user-guide/sql/aggregate_functions.md) |
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| ## General |
| |
| | Function | Description | |
| | --------- | ----------------------------------------------- | |
| | min | Returns the minimum value in a numerical column | |
| | max | Returns the maximum value in a numerical column | |
| | count | Returns the number of rows | |
| | avg | Returns the average of a numerical column | |
| | sum | Sums a numerical column | |
| | array_agg | Puts values into an array | |
| |
| ## Statistical |
| |
| | Function | Description | |
| | -------------------- | ----------------------------------------------------------- | |
| | var / var_samp | Returns the variance of a given column | |
| | var_pop | Returns the population variance of a given column | |
| | stddev / stddev_samp | Returns the standard deviation of a given column | |
| | stddev_pop | Returns the population standard deviation of a given column | |
| | covar / covar_samp | Returns the covariance of a given column | |
| | covar_pop | Returns the population covariance of a given column | |
| | corr | Returns the correlation coefficient of a given column | |
| |
| ## Approximate |
| |
| | Function | Description | |
| | ---------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | |
| | approx_distinct | Returns the approximate number (HyperLogLog) of distinct input values | |
| | approx_median | Returns the approximate median of input values. It is an alias of approx_percentile_cont(x, 0.5). | |
| | approx_percentile_cont | Returns the approximate percentile (TDigest) of input values, where p is a float64 between 0 and 1 (inclusive). It supports raw data as input and build Tdigest sketches during query time, and is approximately equal to approx_percentile_cont_with_weight(x, 1, p). | |
| | approx_percentile_cont_with_weight | Returns the approximate percentile (TDigest) of input values with weight, where w is weight column expression and p is a float64 between 0 and 1 (inclusive). It supports raw data as input or pre-aggregated TDigest sketches, then builds or merges Tdigest sketches during query time. TDigest sketches are a list of centroid (x, w), where x stands for mean and w stands for weight. | |
