Use the "Select by expression" from the Selection Toolbar
with the following expression:
Usually fields like "id" and "fid" are integers, in this case use a slightly difference expression:
Let's assume there were two features selected in the polygon layer 'test'. Afterward the Rule-based symbology was applied using the is_selected() function.
When I unpick the category without the is_selected() the following result will pop up (which will be also true in the Print Composer)
However, IMHO the is_selected() function shows it's real "power&...
Came across this question looking for a slightly different answer, which is to select multiple values in the same column.
I found that rather than doing a whole bunch of 'OR' statements, QGIS (as of 3.10) supports the following syntax:
"<Column Name>" in ('<value 1>', 'value 2>') etc.
There is also a bit lame but working approach using the following expression:
array_contains(array_insert(generate_series(10, 100, 10), 0, 1), "id")
It includes the following functions:
generate_series(), array_insert(), and array_contains().
generate_series(10, 100, 10) produces an array [ 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 ]
Open "Select By Expression" window (Ctrl+F3), enter te following expression:
TR_SEGMENT % 10 = 0 or TR_SEGMENT = 1
You need TR_SEGMENT = 1 because 1 is not multiple of 10. Using TR_SEGMENT % 10 = 0 selects also the feature which has 0 value of TR_SEGMENT if it exists.
PS: % is the modulo operator, which returns the remainder of dividing two ...
Since I wrote the answer to the question you linked I feel mildly obliged to reply... :)
It's not entirely clear from your post what you're trying to do, but is this the correct interpetation?
If there's 2-4 vertices/duplicates, select the feature where vertex_index = 1
If there's > 4 vertices/duplicates, select the feature where vertex_index = 3