approx_percentile aggregate function

Applies to: check marked yes Databricks SQL check marked yes Databricks Runtime

Returns the approximate percentile of the expr within the group.

Syntax 

approx_percentile ( [ALL | DISTINCT] expr, percentile [, accuracy] ) [ FILTER ( WHERE cond ) ]

This function can also be invoked as a window function using the OVER clause.

Arguments

  • expr: A numeric expression.

  • percentile: A numeric literal between 0 and 1 or a literal array of numeric values, each between 0 and 1.

  • accuracy: An INTEGER literal greater than 0. If accuracy is omitted it is set to 10000.

  • cond: An optional boolean expression filtering the rows used for aggregation.

Returns

The aggregate function returns the expression that is the smallest value in the ordered group (sorted from least to greatest) such that no more than percentile of expr values is less than the value or equal to that value.

If percentile is an array, approx_percentile returns the approximate percentile array of expr at percentile. The accuracy parameter controls approximation accuracy at the cost of memory. A higher value of accuracy yields better accuracy, 1.0/accuracy is the relative error of the approximation. This function is a synonym for percentile_approx aggregate function.

If DISTINCT is specified the function operates only on a unique set of expr values.

Examples 

> SELECT approx_percentile(col, array(0.5, 0.4, 0.1), 100) FROM VALUES (0), (1), (2), (10) AS tab(col);
 [1,1,0]

> SELECT approx_percentile(col, 0.5, 100) FROM VALUES (0), (6), (6), (7), (9), (10) AS tab(col);
 6

> SELECT approx_percentile(DISTINCT col, 0.5, 100) FROM VALUES (0), (6), (6), (7), (9), (10) AS tab(col);
 7