Urgent help please

I have a table contains parent and children information, this is not the actual table that I am working with but has similar structure:

ID Name Parent NoOfChildren Age

1     John       NULL         3                     50
2     Mary       1                 0                     20
3     Peter      1                 0                     19
4     David     1                 0                      30
5     Alan       NULL         1                      60
6     Candy     5                0                      25
7     Bobby    NULL         0                      35
8     Vincent    NULL       0                      18

John, age of 50, is the parent of 3 children, Mary, Peter and David. Alan, age of 60 has 1 child, Candy.
Boby has no children.
Vincent has no children.

I am using MySQL so does not support subquery. How do I get the names of the parent when satifiy one of the following conditions:
1) is over 20 years old and have no children 2) is over 20 years old and if his children who are ALL over 20 years old.

Result of the above table:
ID Name Age
5 Alan 60
7 Bobby 35

John is not included because he has child Peter who is 19. Vincent is a parent who is only 18 so also excluded. Received on Tue Aug 19 2003 - 01:54:13 CDT