ST_Quantile-PolarDB(PolarDB)-阿里云帮助中心

Queries the pixel value at one or more quantiles for a raster object.

Prerequisites

Before calling ST_Quantile, calculate the quantiles of the raster object using ST_StatsQuantile.

Syntax

raster ST_Quantile(raster raster_obj,
                   float8[] quantiles default NULL,
                   cstring bands default '',
                   boolean exclude_nodata_value default true,
                   out integer band,
                   out float8 quantile,
                   out float8 value)

Parameters

Parameter	Description
raster_obj	The raster object to query.
quantiles	The quantiles to calculate pixel values for. Valid values: 0.25, 0.5, and 0.75. Specify one or more values as an array. Default value: NULL, which returns all three quantiles.
bands	The band serial numbers to include in the calculation. Supported formats: `'0-2'` (range) and `'1,2,3'` (list). Serial numbers start from 0. Default value: empty string (`''`), which includes all bands.
exclude_nodata_value	Specifies whether to exclude NoData values from the calculation. Default value: true.
band	Output. The serial number of the band.
quantile	Output. The quantile.
value	Output. The pixel value at the quantile.

Examples

Example 1: Query the 0.25 quantile pixel value across all bands

SELECT (ST_Quantile(rast, ARRAY[0.25], '0-2', true)).* FROM rat_quantile WHERE id = 1;

Output:

 band | quantile | value
------+----------+-------
    0 |     0.25 |    11
    1 |     0.25 |    10
    2 |     0.25 |    50
(3 rows)

Example 2: Query all quantiles for band 0

Pass NULL for the quantiles parameter to return all three quantiles (0.25, 0.5, and 0.75).

SELECT (ST_Quantile(rast, NULL, '0', true)).* FROM rat_quantile WHERE id = 1;

Output:

 band | quantile | value
------+----------+-------
    0 |     0.25 |    11
    0 |      0.5 |    11
    0 |     0.75 |    65
(3 rows)