I have many columns, about 30 and each of those has some attributes. I want to merge those columns into one and collect all attributes in a row of columns. I tried with this post Combining Columns QGIS Attribute Table but it is not for what I am looking for.
I have an example in MS Excel that I want that without commas and spaces. Attributes have to be separated with one comma.
With this script, if some fields are empty, I have got