Categories:

Aggregate functions (General) , Window functions

PERCENTILE_CONT¶

Return a percentile value based on a continuous distribution of the input column (specified in order_by_expr). If no input row lies exactly at the desired percentile, the result is calculated using linear interpolation of the two nearest input values. NULL values are ignored in the calculation.

See also:

PERCENTILE_DISC

Syntax¶

Aggregate function

PERCENTILE_CONT( <percentile> ) WITHIN GROUP (ORDER BY <order_by_expr>)
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Window function

PERCENTILE_CONT( <percentile> )
  WITHIN GROUP (ORDER BY <order_by_expr>)
  OVER ( [ PARTITION BY <expr3> ] )
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Arguments¶

percentile

The percentile of the value that you want to find. The percentile must be a constant between 0.0 and 1.0. For example, if you want to find the value at the 90th percentile, specify 0.9.

order_by_expr

The expression (typically a column name) by which to order the values. For example, if you want to want to find the student whose math SAT score is at the 90th percentile, then specify the column containing the math SAT score.

Note that this is also implicitly the column from which the returned value is chosen. For example, if you order by math SAT scores, then the result is one of the math SAT scores. You cannot order by one column and get a percentile value for a different column.

expr3

This is the optional expression used to group rows into partitions.

Returns¶

Returns the value that is at the specified percentile. If no input row lies exactly at the desired percentile, the result is calculated using linear interpolation of the two nearest input values.

Note

If a group contains only one value, then that value will be returned for any specified percentile (e.g. both percentile 0.0 and percentile 1.0 will return that one row).

Usage notes¶

  • The percentile argument to the function must be a constant.

  • DISTINCT is not supported for this function.

  • The function PERCENTILE_CONT interpolates between the two closest values, while the function PERCENTILE_DISC chooses the closest value rather than interpolating.

  • When this function is called as a window function, it does not support:

    • An ORDER BY clause within the OVER clause.

    • Explicit window frames.

Examples¶

The following example shows the values at the 25th percentile (0.25) within various groups:

Create and populate a table with values:

create or replace table aggr(k int, v decimal(10,2));
insert into aggr (k, v) values
    (0,  0),
    (0, 10),
    (0, 20),
    (0, 30),
    (0, 40),
    (1, 10),
    (1, 20),
    (2, 10),
    (2, 20),
    (2, 25),
    (2, 30),
    (3, 60),
    (4, NULL);
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Run a query and show the output (note that some values are exact and some are interpolated):

select k, percentile_cont(0.25) within group (order by v) 
  from aggr 
  group by k
  order by k;
+---+-------------------------------------------------+
| K | PERCENTILE_CONT(0.25) WITHIN GROUP (ORDER BY V) |
|---+-------------------------------------------------|
| 0 |                                        10.00000 |
| 1 |                                        12.50000 |
| 2 |                                        17.50000 |
| 3 |                                        60.00000 |
| 4 |                                            NULL |
+---+-------------------------------------------------+
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