sql query

Question

Hi all,
I have a  table like this:

Table1

idname        comment

1test        null   

2test1        abc

3test1        def

4TEST2abc

5test3        abc

6test3        def

7TEST4abc

I would like to get all rows

1. where comment='null'

2. if name (Example: test1) has 'abc' and 'def' in comment column than show only where comment= 'def'

3. if name has only 'abc' than show that row


the output should be like this:

idname        comment

1test        null

2test1        def

3TEST2abc

4test3        def

5TEST4abc

How can I write the query for this scenario?


Thanks,
Darma