Compare datasets - wrong output

[roundedhexagon]

Hi guys, Please be tender, I am pretty new to n8n My goal is to build a tool which I can use to monitor when a new property is added.

Most of the automatization is already done: I use HTML node to get the source of tha page, manipulate it using JavaScript and also store the properties ’URLs as a unique ID to track which is a new property and which one is an old one.

So far, pretty straightforward, but I can’t figure out one messy part: identifying the newly added properties. Using the code node I already converted to this format:

{
"id": 
1,
"title": 
"71 áras beltelek a Lina kanyarban, ház építésre is alkalmas",
"description": 
"Eladó 71 áras telek a Lina kanyarban, közvetlenül a forrás mellett, bejárattal a főútról, ...",
"location": 
"Csikszereda",
"price": 
"24 000 EUR",
"url": 
"/aprohirdetes/59-telek/170005-71-aras-beltelek-a-lina-kanyar.html"
}

Also, I use Data tables to store the already indexed entries

{
"id": 
3,
"createdAt": 
"2025-10-17T20:54:11.077Z",
"updatedAt": 
"2025-10-17T21:01:31.850Z",
"HirdetesID": 
"/aprohirdetes/59-telek/926619-szekelyudvarhelyi-panoramas-pu.html"

I tried to use the Compare datasets node to compare the two sources and identify the newly added properties, but I can’t make it work correctly:

If you take a look to the output schema mode, it shows one result (instead of two, because there is 28 url in the Data tables and 30 in the html output), and if I switch to table or JSON view it shows 30 results. I also added a telegram node, but when I execute the step it sends me 30 messages instead of the newly added 2 properties’ notification. What am I doing wrong? Probably it has to be something straightforward that I can’t figure out. Thank you for your help!

You can find the wokflow json here (it was too long to post it here): Compare datasets · GitHub

[mohamed3nan]

Hi @roundedhexagon

Why aren’t you linking the Get row(s) node?

After I linked it, I got this output:

Maybe this is what you’re looking for?

[mohamed3nan]

Also for your information, there’s another built-in node you can use to get only the new items in each execution without needing to save them in a database and compare manually..

It’s the Remove Duplicates node:

Remove Duplicates node documentation | n8n Docs

You can use it like this:

and each new excution you will only get the new items:

It’s easy to use, especially if your use case is simple and straightforward,
for example, when you just want to get only the new items in each execution compared to the previous one..

[roundedhexagon]

This solved the issue! Thank you for your help @mohamed3nan I have no idea what I haven’t connected the data tables node to the trigger! That solved my issue instantly