ST_X
Descriptionβ
When the point is a valid POINT type, returns the corresponding X coordinate value.
Sytaxβ
ST_X( <point>)
Parametersβ
Parameter | Description |
---|---|
<point> | The geometric object from which to extract the X coordinate. It must be a valid POINT type (2D point), where the X (longitude) range is [-180, 180] and the Y (latitude) range is [-90, 90]. |
Retuen valueβ
The X value in the geometric coordinates, of type double-precision floating-point number (Double).
- Returns the X coordinate of the point (double-precision floating-point number, Double) if the input is a valid POINT object.
- Returns NULL if the input is NULL, a non-POINT type object, an empty point (POINT EMPTY), or an invalid point (e.g., 3D point).
Exampleβ
Extract X coordinate of a valid point
SELECT ST_X(ST_Point(24.7, 56.7));
+----------------------------+
| st_x(st_point(24.7, 56.7)) |
+----------------------------+
| 24.7 |
+----------------------------+
Input is an empty point (POINT EMPTY)
mysql> SELECT ST_X(ST_GeometryFromText("POINT EMPTY"));
+------------------------------------------+
| ST_X(ST_GeometryFromText("POINT EMPTY")) |
+------------------------------------------+
| NULL |
+------------------------------------------+
Input is a 3D point (not supported)
mysql> SELECT ST_X(ST_GeometryFromText("POINT (10 20 30)"));
+-----------------------------------------------+
| ST_X(ST_GeometryFromText("POINT (10 20 30)")) |
+-----------------------------------------------+
| NULL |
+-----------------------------------------------+
Input is NULL
mysql> SELECT ST_X(NULL);
+------------+
| ST_X(NULL) |
+------------+
| NULL |
+------------+
Longitude out of range
mysql> SELECT ST_X(ST_Point(244.7, 56.7));
+-----------------------------+
| ST_X(ST_Point(244.7, 56.7)) |
+-----------------------------+
| NULL |
+-----------------------------+
Latitude out of range
mysql> SELECT ST_X(ST_Point(44.7, 156.7));
+-----------------------------+
| ST_X(ST_Point(44.7, 156.7)) |
+-----------------------------+
| NULL |
+-----------------------------+