ST_{X|Y|Z|T}Max

Syntax

float8 ST_XMax(boxndf box);
float8 ST_YMax(boxndf box);
float8 ST_ZMax(boxndf box);
timestamp ST_TMax(boxndf box);

Parameters

Description

Each function extracts the upper bound of a boxndf bounding box along a single dimension:

• ST_XMax and ST_YMax return a float8 value. If the bounding box has no X or Y dimension, the function returns NaN.

• ST_ZMax returns a float8 value. If the bounding box has no Z dimension, the function returns NaN.

• ST_TMax returns a timestamp value. If the bounding box has no T dimension, the function returns -infinity.

Use the return value to detect whether a dimension is present: NaN indicates a missing spatial dimension (X, Y, or Z); -infinity indicates a missing temporal dimension (T).

Examples

Query the maximum T value of a 2D+T bounding box

ST_MakeBox2dt creates a bounding box with X, Y, and T dimensions. Querying ST_TMax returns the upper timestamp bound.

select ST_tmax(ST_MakeBox2dt(0,0,'2000-01-01'::timestamp, 20,20, '2020-01-01'::timestamp));
       st_tmax
---------------------
 2020-01-01 00:00:00

Query a missing dimension

The same bounding box has no Z dimension, so ST_ZMax returns NaN. A box with no T dimension returns -infinity from ST_TMax.

select ST_zmax(ST_MakeBox2dt(0,0,'2000-01-01'::timestamp, 20,20, '2020-01-01'::timestamp));
 st_zmax
---------
     NaN

select ST_tmax(ST_MakeBox2d(0,0, 20,20));
  st_tmax
-----------
 -infinity

What's next

• ST_{X|Y|Z|T}Min — returns the minimum coordinate value along a specified dimension

• ST_MakeBox2d — creates a 2D bounding box from two points

• ST_MakeBox2dt — creates a 2D+T bounding box from two spatiotemporal points