Question

I have an SQLite database with a simple table of Persons.

Each row represents a person and has four columns: the primary key (id), one for the name, one for the age and one for the parent (points to the primkey id, is NULL if the person has no parent).

Now, I just want to list all those persons sorted on age and have the children grouped with their parent.

For example: (Name, Age)

Dan, 18
Eva, 21
- Bill, 4
- Bull, 7

Steve, 38
Richard, 63
- Ann, 19
- Clara, 39

Vera, 70  

This sounds simple, but I cannot figure out the SQL statement 🙁
Thanks in advance!

/John

Answer 1

I recommend you to split this into two queries.

First, get a list of parents:

SELECT *
FROM Persons
WHERE id IN (SELECT parent FROM Persons)
ORDER BY (age, id)

Then get a properly sorted list of children:

SELECT Child.*
FROM Persons AS Child
     JOIN Persons AS Parent ON (Parent.id = Child.parent)
ORDER BY (Parent.age, Parent.id, Child.age, Child.id)

The two lists can then easily be merged on the id/parent since they are both sorted first by parent’s age.