diff --git a/content/shared/sql-reference/functions/aggregate.md b/content/shared/sql-reference/functions/aggregate.md index 45630de2f..dcc50a99c 100644 --- a/content/shared/sql-reference/functions/aggregate.md +++ b/content/shared/sql-reference/functions/aggregate.md @@ -1492,7 +1492,7 @@ GROUP BY room ### approx_median Returns the approximate median (50th percentile) of input values. -It is an alias of `approx_percentile_cont(x, 0.5)`. +It is an alias of `approx_percentile_cont(0.5) WITHIN GROUP (ORDER BY expression)`. ```sql approx_median(expression) @@ -1529,15 +1529,18 @@ GROUP BY room Returns the approximate percentile of input values using the t-digest algorithm. ```sql +approx_percentile_cont(percentile [, centroids]) WITHIN GROUP (ORDER BY expression) +-- OR approx_percentile_cont(expression, percentile, centroids) ``` ##### Arguments -- **expression**: Expression to operate on. - Can be a constant, column, or function, and any combination of arithmetic operators. - **percentile**: Percentile to compute. Must be a float value between 0 and 1 (inclusive). - **centroids**: Number of centroids to use in the t-digest algorithm. _Default is 100_. + A higher number results in more accurate approximation but requires more memory. +- **expression**: Expression to operate on. + Can be a constant, column, or function, and any combination of arithmetic operators. If there are this number or fewer unique values, you can expect an exact result. A higher number of centroids results in a more accurate approximation, but @@ -1551,7 +1554,7 @@ _The following example uses the {{< influxdb3/home-sample-link >}}._ ```sql SELECT room, - approx_percentile_cont(temp, 0.99) AS "99th_percentile" + approx_percentile_cont(0.99) WITHIN GROUP (ORDER BY temp) AS "99th_percentile" FROM home GROUP BY room ``` @@ -1570,6 +1573,8 @@ Returns the weighted approximate percentile of input values using the t-digest algorithm. ```sql +approx_percentile_cont_with_weight(weight, percentile [, centroids]) WITHIN GROUP (ORDER BY expression) +-- OR approx_percentile_cont_with_weight(expression, weight, percentile) ``` @@ -1580,6 +1585,8 @@ approx_percentile_cont_with_weight(expression, weight, percentile) - **weight**: Expression to use as weight. Can be a constant, column, or function, and any combination of arithmetic operators. - **percentile**: Percentile to compute. Must be a float value between 0 and 1 (inclusive). +- **centroids**: Number of centroids to use in the t-digest algorithm. _Default is 100._ + A higher number results in more accurate approximation but requires more memory. {{< expand-wrapper >}} {{% expand "View `approx_percentile_cont_with_weight` query example" %}} @@ -1589,7 +1596,7 @@ _The following example uses the {{< influxdb3/home-sample-link >}}._ ```sql SELECT room, - approx_percentile_cont_with_weight(temp, co, 0.99) AS "co_weighted_99th_percentile" + approx_percentile_cont_with_weight(co, 0.99) WITHIN GROUP (ORDER BY temp) AS "co_weighted_99th_percentile" FROM home GROUP BY room ```