Combine two dup rows into one

1

Hello,

How do I combine two rows dataset into one row? For example:

from this dataset:

Select Row#1,Column1, Column2, Column3
from database

Row#1 Column1 Column2 Column3
1 A B C
2 A B D

to:
Row#1 Column1 Column2 Column3
1 A B C,D

Thank you

2

based on what is the condition to combine ?

Please post more sample data and the expected result