diff --git a/docs/en/12-taos-sql/10-function.md b/docs/en/12-taos-sql/10-function.md index 8ab5176aab0a3cd9a2dc4395febbf6ddc8f595f3..4504456cd7fb29a7147479065623c24d7516491f 100644 --- a/docs/en/12-taos-sql/10-function.md +++ b/docs/en/12-taos-sql/10-function.md @@ -795,19 +795,23 @@ HISTOGRAM(expr,bin_type, bin_description, normalized) ### PERCENTILE ```sql -PERCENTILE(expr, p) +PERCENTILE(expr, p [, p1] ...) ``` **Description**: The value whose rank in a specific column matches the specified percentage. If such a value matching the specified percentage doesn't exist in the column, an interpolation value will be returned. -**Return value type**: DOUBLE +**Return value type**: This function takes 2 minumum and 11 maximum parameters, and it can simultaneously return 10 percentiles at most. If 2 parameters are given, a single percentile is returned and the value type is DOUBLE. + If more than 2 parameters are given, the return value type is a VARCHAR string, the format of which is a JSON ARRAY containing all return values. **Applicable column types**: Numeric **Applicable table types**: table only -**More explanations**: _p_ is in range [0,100], when _p_ is 0, the result is same as using function MIN; when _p_ is 100, the result is same as function MAX. +**More explanations**: +- _p_ is in range [0,100], when _p_ is 0, the result is same as using function MIN; when _p_ is 100, the result is same as function MAX. +- When calculating multiple percentiles of a specific column, a single PERCENTILE function with multiple parameters is adviced, as this can largely reduce the query response time. + For example, using SELECT percentile(col, 90, 95, 99) FROM table will perform better than SELECT percentile(col, 90), percentile(col, 95), percentile(col, 99) from table. ## Selection Functions diff --git a/docs/zh/12-taos-sql/10-function.md b/docs/zh/12-taos-sql/10-function.md index c44c09d10c115a41efd22048d4fdafdc85370ac2..bc51a51209f59cc8941e147591427af20ae4ea44 100644 --- a/docs/zh/12-taos-sql/10-function.md +++ b/docs/zh/12-taos-sql/10-function.md @@ -798,18 +798,22 @@ HISTOGRAM(expr,bin_type, bin_description, normalized) ### PERCENTILE ```sql -PERCENTILE(expr, p) +PERCENTILE(expr, p [, p1] ... ) ``` **功能说明**:统计表中某列的值百分比分位数。 -**返回数据类型**: DOUBLE。 +**返回数据类型**: 该函数最小参数个数为 2 个,最大参数个数为 11 个。可以最多同时返回 10 个百分比分位数。当参数个数为 2 时, 返回一个分位数, 类型为DOUBLE,当参数个数大于 2 时,返回类型为VARCHAR, 格式为包含多个返回值的JSON数组。 **应用字段**:数值类型。 **适用于**:表。 -**使用说明**:*P*值取值范围 0≤*P*≤100,为 0 的时候等同于 MIN,为 100 的时候等同于 MAX。 +**使用说明**: + +- *P*值取值范围 0≤*P*≤100,为 0 的时候等同于 MIN,为 100 的时候等同于 MAX; +- 同时计算针对同一列的多个分位数时,建议使用一个PERCENTILE函数和多个参数的方式,能很大程度上降低查询的响应时间。 + 比如,使用查询SELECT percentile(col, 90, 95, 99) FROM table, 性能会优于SELECT percentile(col, 90), percentile(col, 95), percentile(col, 99) from table。 ## 选择函数