ST_GeogFromText-PolarDB(PolarDB)-阿里云帮助中心

Returns a geography value from a Well-Known Text (WKT) or Extended Well-Known Text (EWKT) representation.

Syntax

geography ST_GeogFromText(text eWKT);

Parameters

Parameter	Description
`eWKT`	A WKT or EWKT string representing a geographic shape. To specify a spatial reference identifier (SRID), prefix the string with `SRID=<value>;` (for example, `SRID=4326;POINT(116 40)`).

Usage notes

If no SRID is specified, the default SRID 4326 (WGS84) is used.
ST_GeogFromText is an alias for ST_GeographyFromText. Both functions are equivalent.
Coordinates are in longitude-latitude order (longitude first, latitude second).

Longitude comes first in the coordinate pair—this is the most common source of errors when working with ST_GeogFromText. Longitude represents the x-axis; latitude represents the y-axis.

Examples

Construct a geography object with the default SRID

When no SRID is specified, SRID 4326 is used automatically.

SELECT ST_SRID(ST_GeogFromText('POINT(116 40)'));
 st_srid
---------
    4326
(1 row)

Construct a geography object with a specified SRID

Prefix the WKT string with SRID=<value>; to use a non-default coordinate system.

SELECT ST_SRID(ST_GeogFromText('SRID=4256;POINT(116 40)'));
 st_srid
---------
    4256
(1 row)