Selecting new records using values inside previous selected rows in QGIS?

Question

I am trying to create a selection. First, I select records which have Null value in "Status" column ("Status" is NULL"). Then it starts to be a bit tricky. I want to select all the records which have the same number as selected "Status" records. Is it possible to do it in QGIS?

First, I select null values using "Status" is NULL expression.

Then I need to add something to take ID values and use it to create a new selection.

The final selection should look like that:

I am using QGIS 2.16.

Answer 1

You may run this code from the Python Console (it works on the active layer):

layer = iface.activeLayer()
query_1 = '"Status" is NULL'
selection = layer.getFeatures(QgsFeatureRequest().setFilterExpression(query_1))
selected_ids = [k["ID"] for k in selection]

ids = []
for feat in layer.getFeatures():
    if feat["ID"] in selected_ids:
        ids.append(feat.id())
layer.setSelectedFeatures([l for l in ids])

You will obtain the desired output: