I create a view with two arguments: Taxonomy ID (tid) and Node NID (nid). I leave the default settings for tid and set a default argument for nid to a fixed value (let's say: 1). The tid argument is configured so that all values are shown in case it is not present. This should show all nodes except the one with NID 1.
BUT: This only works if the NID argument is the first argument. If it's the second argument, it is excluded from the query:
Query with nid as first argument:
SELECT node.nid AS nid FROM node node WHERE node.nid != 1 OR node.nid IS NULL
Query with nid as second argument:
SELECT node.nid AS nid FROM node node
I'm wondering why that is? What I want to accomplish is actually to exclude the result of one view from another. To do that, I add nid as an argument, get the nids of a different view and tell views to exclude them. That works just fine, but only if nid is the first argument. But I need to have taxonomy as the first argument and I don't understand why that excludes my nid argument.
Although in a different context, I think I had the same problem here: https://stackoverflow.com/questions/20248929/filter-a-drupal-view-displayed-in-a-panel-by-taxonomy-term-depending-on-domain