* What is the average age of a person?
select avg(age) from person;
51.85



*  Who is the oldest person(s)?
select name from person where age = (select max(age) from person);
+------+
| name |
+------+
| Ed   |
| Edna |
+------+



* What is the average age of a parent?
select avg(age) from person where id in (select parent from related);
55.4



* Are there more men or women?
select gender, count(gender) from person group by gender;
Male = 6, Female = 8



* How many people have children?
select count( distinct parent) from related;
10







* Who is Pebble's mother?
select PARENT.name from person CHILD, person PARENT, related where CHILD.name = "Pebbles" and CHILD.id = child and parent = PARENT.id and PARENT.gender = 'f';
Wilma



* List Pebble's parents and their ages?
select name, age from person where id in (select parent from related where child = (select id from person where name = "Pebbles"));
+-------+------+
| name  | age  |
+-------+------+
| Fred  |    2 |
| Wilma |   42 |
+-------+------+




* How many children did Pebbles have?
select count(child) from person, related where name = "Pebbles" and parent=id;
2