How to get single row from multiple rows having same ID?

I have multiple rows for same ID. How to display any one row per unique ID?

I tried

select Col_1, Col_2, Col_3 from Table group by Col_1. 

But this throws error saying, Col_2 and Col_3 is not in group by clause ( I wonder if syntax is wrong )

this is the given table

Col_1  Col_2  Col_3
1        A       B
1        B       A
2        C       D
2        D       C

Expected Output

Col_1  Col_2  Col_3
1        A       B
2        C       D

Answer

You are very close… when using group by , columns that are not part of the grouping statement must be part of an aggregate function. As such you can do something like:

select Col_1, Max(Col_2), Max(Col_3) from Table group by Col_1

I used the max Aggregation function here, but you can use any function you want. The above should get you what you are looking for and should run on most DBs