Select query in SQL row and all related rows?

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SQL

SQL-Server

hi all
i have table name mytable
has two column called clmnA, clmnB
values
1,0
2,1
3,2
5,4

1 is connected to no 0
2 is connected to no 1
3 is connected to no 2
and so on.....

i need to select where clmna = 3
and reslut get all connectd values to this number

the result must be 2,1,0

What I have tried:

i dont try any thing to solve this problem