SQL Select Rows that have same column value

Question

I Have following table, I Would like to Select rows that have same value in Zone field for the same Line number.

Id	Line	Name	Zone
1	10	A	2
2	10	B	2
3	15	C	3
4	15	D	4
5	17	E	5
6	17	F	5
7	17	G	6
8	20	H	7
9	20	I	7

Result should be:

Id	Line	Name	Zone
1	10	A	2
2	10	B	2
8	20	H	7
9	20	I	7

What's the correct way to query this?

Answer 1

One way is using EXISTS

Select Id, Line, Name, Zone
from tbl t
where not exists (
      select 1 
      from tbl t2 
      where t2.Line = t1.Line and t2.Zone <> t1.Zone)