KQL: Merge 2 column of the same table

I'm trying to merge 2 column of the same table into 1 column.

from

into

I'm a KQL newbie. My goal is to have a query, extract information of two column, merge the two columns into a new one and perform some string manipulation to extract the data that I want (domain names from emails addresses)

I have try with join, extend and summarize.

my current unworking query is the following (MS Sentinel):

<code>let emaildomain = dynamic(['aaa', 'bbb']);
EmailEvents
| where RecipientEmailAddress in (emaildomain) or SenderFromDomain in (emaildomain)
| extend mailsaddreses = RecipientEmailAddress, SenderFromAddress
| project mailsaddreses
| project splitted = split(mailsaddreses, '@')
| project domainnames = splitted[1]
| distinct tostring(domainnames)
| where domainnames !has "myCompany"
</code>

the simplified query is the following

<code>let emaildomain = dynamic(['AAA.com']);
EmailEvents
| where RecipientEmailAddress in (emaildomain) or SenderFromDomain in (emaildomain)
| distinct RecipientEmailAddress, SenderFromAddress</code>

where I want "RecipientEmailAddress", "SenderFromAddress" to be in the same column

Thank you in advance for your help

you can use the union operator.

for example:

let T = datatable(Col1: int, Col2: int)
[
    1, 4,
    2, 5,
    3, 6
]
;
T
| project Col3 = Col1
| union (T | project Col3 = Col2)