Returns the minimum boundary value of a boxndf bounding box along the X, Y, Z, or T dimension.
Syntax
float8 ST_XMin(boxndf box);
float8 ST_YMin(boxndf box);
float8 ST_ZMin(boxndf box);
timestamp ST_TMin(boxndf box);| Function | Returns | Description |
|---|---|---|
ST_XMin | float8 | Minimum X coordinate of the bounding box |
ST_YMin | float8 | Minimum Y coordinate of the bounding box |
ST_ZMin | float8 | Minimum Z coordinate of the bounding box |
ST_TMin | timestamp | Earliest timestamp of the bounding box |
Parameters
| Parameter | Type | Description |
|---|---|---|
box | boxndf | The bounding box to query |
Usage notes
The functions behave differently depending on whether the requested dimension exists in the bounding box:
X, Y, or Z dimension missing — returns
NaN.T dimension missing — returns
-infinity.
Before calling a Min function, verify that the bounding box has the target dimension. Calling ST_ZMin on a 2D+T box returns NaN, not an error. Calling ST_TMin on a 2D box returns -infinity, not an error.
To check whether a dimension exists before querying its minimum value, use the corresponding dimension accessor or spatial constructor that matches your box type. For example, ST_MakeBox2dt creates a box with X, Y, and T dimensions but no Z dimension.
Examples
Example 1: Query the minimum X value of a 2D+time bounding box
select ST_xmin(ST_MakeBox2dt(0,0,'2000-01-01'::timestamp, 20,20, '2020-01-01'::timestamp));
st_xmin
---------
0Example 2: Query the minimum Z value of a 2D+time bounding box
The box was created with ST_MakeBox2dt, which has no Z dimension, so the result is NaN.
select ST_zmax(ST_MakeBox2dt(0,0,'2000-01-01'::timestamp, 20,20, '2020-01-01'::timestamp));
st_zmin
---------
NaN
-- NaN indicates the Z dimension does not exist in this bounding box.Example 3: Query the minimum T value of a 2D bounding box
The box was created with ST_MakeBox2d, which has no T dimension, so the result is -infinity.
select ST_tmax(ST_MakeBox2d(0,0, 20,20));
st_tmin
-----------
-infinity
-- -infinity indicates the T dimension does not exist in this bounding box.