[tip] search for / selecting NO keywords (selection photos without a keyword)

Question

Probably it is old news but I couldn't find it here that fast.
I have 20.000 photos, some have a keyword(s) some have not. So I searched for a selection of photographs without a keyword. But there is none.
The trick is to add a special keyword you normally not use like (only) "_" (underscore) to all photos without a keyword. But there is no way to select photos wihtout a keyword... So I came up with a two step strategy and this trick only cost 2-3 minutes with 20.000 photos:
Add the "_" keyword to all you photos.
Select all photos with a real keyword by shift clicking on all keywords tags except "_".
Remove the "_" keyword from those photos.
Now select the "_" keyword or search on the "_" keyword.
A how to, in 14 steps:
1. Hit G, goto library (in left panel) and click on "all photographs"
2. Select all photos by pressing ctrl-a
3. Wait till LR is ready displaying all used keywords in the right keywords panel
4. In right panel under keywording/keyword tags add the keyword "_"
5. Wait till LR is ready updating all your photos (20.000 photos: 1 minute)
6. Goto "Keyword tags" in the left panel
7. Select the (suppose the second) keyword just after the "_" keyword by left clicking.
8. Scroll down till the end in the keyword list
9. Now, shift click on the last keyword
10. You now selected all keywords except the "_" keyword and all are highlihted
11. Select all photo's (ctrl-a)
12. Wait till LR shows all the keywords in the Keywording/keyword tags panel on the right
check: the keyword "_" should have no asterix like "_*" if so: goto step 1!
13. Remove the "_" keyword and press enter
14. Wait till LR is ready
From now on while selecting the "_" keyword or searching on the keyword "_" LR will only show the photos without a (real) keyword.
Of course, as soon as you add keyword(s) to your foto(s) you have to delete the "_" keyword.
Speed tip: when starting keywording, select the photo you like to add real keywords, ctrl-k brings you directly to the keyword tags panel in edit mode, hit backspace (to delete the "_" keyword and start typing your keywords and hit enter or tab when done. Then immediately (of course) the photo dissapears from your "_" keyword selection photos and the next photo is selected and is waiting for you to hit ctrl-k and start again. Look mam, "no mouse used!"
Have fun!

Answer 1

>I have 20.000 photos, some have a keyword(s) some have not. So I searched for a selection of photographs without a keyword. But there is none.
There is actually, and it is much simpler:
Using the Find Panel, choose Text: Keywords and Rule: Are Empty.