ST_AsText
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Name

ST_AsText — Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.

Synopsis

text ST_AsText(geometry g1);

text ST_AsText(geometry g1, integer maxdecimaldigits = 15);

text ST_AsText(geography g1);

text ST_AsText(geography g1, integer maxdecimaldigits = 15);

Descrizione

Returns the OGC Well-Known Text (WKT) representation of the geometry/geography. The optional maxdecimaldigits argument may be used to limit the number of digits after the decimal point in output ordinates (defaults to 15).

To perform the inverse conversion of WKT representation to PostGIS geometry use ST_GeomFromText.

[Note]

The standard OGC WKT representation does not include the SRID. To include the SRID as part of the output representation, use the non-standard PostGIS function ST_AsEWKT
[Warning]

The textual representation of numbers in WKT may not maintain full floating-point precision. To ensure full accuracy for data storage or transport it is best to use Well-Known Binary (WKB) format (see ST_AsBinary and maxdecimaldigits).
[Warning]

Using the maxdecimaldigits parameter can cause output geometry to become invalid. To avoid this use ST_ReducePrecision with a suitable gridsize first.

Availability: 1.5 - support for geography was introduced.

Enhanced: 2.5 - optional parameter precision introduced.

Questo metodo implementa le OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

Questo metodo implementa la specifica SQL/MM. SQL-MM 3: 5.1.25

Questo metodo supporta le Curve e le Circular String.

Esempi

SELECT ST_AsText('01030000000100000005000000000000000000
000000000000000000000000000000000000000000000000
F03F000000000000F03F000000000000F03F000000000000F03
F000000000000000000000000000000000000000000000000');

    st_astext
--------------------------------
 POLYGON((0 0,0 1,1 1,1 0,0 0))

Full precision output is the default.

SELECT ST_AsText('POINT(111.1111111 1.1111111)'));
    st_astext
------------------------------
 POINT(111.1111111 1.1111111)

The maxdecimaldigits argument can be used to limit output precision.

SELECT ST_AsText('POINT(111.1111111 1.1111111)'), 2);
    st_astext
--------------------
 POINT(111.11 1.11)