Retreiving info from another layer

Question

I have two shapefiles:

1. street (polyline) listing of all streets in one village with fields 'streetId', 'Streetlength' (virtual field)

2. streetpanel listing of all panels displaying street name with fields 'panelid' , 'streetref' making a reference to the streetid of table 1

I want to put in table 2 a calculated field that retrieves the street length the panel refers to.

I am not a real expert in QGIS/Python, so I looked at what I can do with existing functions (getfeature(), attributes(), aggregate(),...) but I do not know how to address this.

How can I approach this problem?

Answer 1

Layer 1 is called street, its id being streetid and has a column streetlength

Layer 2 has a field called streetref, refering to the streetid in Layer1

Add a computed column with this code in Layer2:

attributes(get_feature('street','streetid', "streetref" ))['streetlength']

Gets the feature from layer street where attribute streetid is equal to "streetref" (from Layer2)

And gets the streetlength attribute from that feature