Symbol only overall border of multiple polygon features

[EDUARDOARDILARINCON]

Hi Everyone, I'm trying to apply symbology to a feture class, inside of tha feature class there are multiple polygons that correspond to one same group, when I apply simbology to the layer it looks like this:

However what I'm looking for is this:

I've done that through the merge tool, but I was wondering if is there any way to get the same result without modifying the original features (or creating another feature class)?
Like creating the simbology only for the outer line of the entire group of polygons.

Thanks a lot!

Eduardo

[jcarlson]

There's not a "nice" way to do it, but here's a hacky approach:

Starting with some contiguous polygons:

Duplicate the layer, then on the original, set it's masking source to the duplicate.

Note, though, that you're only going to get the bits of your symbology that fall outside of the features, so your stroke / marker lines are going to get clipped in half.

It's a shame, because QGIS has had "merged polygons" as a symbol style for ages, and it's such a useful thing to avoid throwaway merge layers.

[jcarlson]

If your data is in an enterprise geodatabase, you could also use spatial SQL like ST_UNION(geometry) with a groupby statement to get your polygons to all behave as though they are merged, without modifying the original source data.

[PaulinaKarkauskaite]

@EDUARDOARDILARINCON 

You can enable control points and use the suppress effect to hide the segments without changing the underlying geometry. By inserting control points, you can mark the segments that should be hidden.

Below are links to the help topics, but let me know if you have questions to the workflow:

Enable control points or change symbology

Add a global effect to an entire symbol - add the suppress effect to the layer

Edit control points - mark the segments that should be suppressed (masked).

Hope this helps.

Thank you,

Paulina