Using concat(field1, field2) concatenates 0 instead of empty string ('') if any of the fields is NULL

[tudorbarascu]

Describe the bug

How to Reproduce
Using concat(field1, field2) concatenates 0 instead of empty string ('') if field2 is NULL.
The field2 is integer.

For a field1 of text type having value test, field2 type integer and NULL (no value).
A label using concat(field1,field2) expression returns test0 instead of the expected test (adds a 0 instead of an empty string)

I can expand the expression with an IF statement to solve it but.. it's a bug, right?

QGIS and OS versions

QGIS 3.10.5 Windows and Debian Bullseye

[troopa81]

I failed to reproduce. In 3.10 and master on Debian bullseye with GeoPackage data.

I tried also with Integer64 and get the same result.

Could you share data sample/project?

[tudorbarascu]

Hi @troopa81 I forgon to mention it's a Postgis database, didn't test with anything else. But for Postgis I can always replicate:

Create the following table:

CREATE TABLE bad_concat (id serial PRIMARY KEY, field1 text, field2 integer);

INSERT INTO bad_concat (field1) SELECT 'something';

concat(field1,field2) returns something0

Thanks for working on this.