Adding field with geometry WKT in QGIS

Question

I have a shapefile with polygons and want to add an attribute field with the WKT in QGIS 3.4.

The function geom_to_wkt in the Field Calculator isn't working and I don't know how to do it. Any ideas?

Answer 1

First, create a new text field as commented above with a high numbers of chararcters. Then use the Field Calculator to convert the geometry to WKT as described in the comments:

The field will hold the geometry as seen in the preview above:

Answer 2

Tested on QGIS 2.18 and QGIS 3.4

I can suggest using a "Virtual Layer" through Layer > Add Layer > Add/Edit Virtual Layer...

Let's assume there is a polygon layer "districts" with its attribute table accordingly, see image below.

With the following Query by means of QGIS native geometry function geom_to_wkt, it is possible to achieve the result

SELECT *, geom_to_wkt(geometry) AS wkt
FROM "districts"

The output Virtual Layer will maintain original geometry and all initial attributes including a new, namely 'wkt'.

The alternative query will contain ST_AsText parameter.

It returns the Well-Known Text representation of the geometry/geography. Optional argument may be used to reduce the maximum number of decimal digits after floating-point used in the output (defaults to 15).

SELECT *, ST_AsText(geometry) AS wkt
FROM "districts"