Delete data from child tables - sql

Question

I have 2 tables:
"customers" and "addresses". A customer can have several addresses, so they have an "n:m" relationship.
For this reason, I also have the table "customer-addr".
This is how my tables look like:
+---------------+
+-----------+ | customer_addr |
| customers | +---------------+ +-----------+
+-----------+ | id | | addresses |
| id | <---> | cid | +-----------+
| name | | aid | <---> | id |
+-----------+ +---------------+ | address |
+-----------+
I need to update all customer-data incl. all addresses. For this reason I thought about deleting all existing addresses first, then updating the customer-table, and after that, I create every address new.
My question: How can I delete all existing addresses from one customer efficiently? (I have to remove rows from 2 tables).
Is there a single-statement I can use? (Without the cascade-method, this is too risky)
Or can I do it with 2 statements, without using subselects?
What's the best approach for this?
Notice that I'm using postgresql
Edit:
My whole database-design is more complex, and the address-table is not only a child from "customers" but also from "suppliers","bulkbuyers",..
Every address belongs to only one customer OR one supplier OR one bulkbuyer.
(No address is used by more than one parent / no address-sharing)
Ever customer/supplier/.. can have multiple addresses.
For this reason, the edited solution from zebediah49 won't work, because it would also delete all addresses from every supplier/bulkbuyer/...

Answer 1

I would use a writable CTE also called data-modifying CTE in PostgreSQL 9.1 or later:
WITH del AS (
DELETE FROM customer_addr
WHERE cid = $kill_this_cid
RETURNING aid
)
DELETE FROM addresses a
USING (SELECT DISTINCT aid FROM del) d
WHERE a.id = d.aid;
This should be fastest and safest.
If (cid, aid) is defined UNIQUE in customer_addr you don't need the DISTINCT step:
...
DELETE FROM addresses a
USING del d
WHERE a.id = d.aid;

Answer 2

EDIT:
Got it; this is safer because of the risk of two customers sharing an address anyway:
DELETE FROM customer_addr WHERE cid = $TARGET_CID;
DELETE FROM addresses WHERE id NOT IN (SELECT aid FROM customer_addr);
First, delete all references, then delete all unreferenced addresses.
Note that you could, for example, only do the first step, and run the "cleanup" second step at a later time.
I would suggest a two step transaction:
DELETE FROM addresses WHERE id IN (SELECT ca.aid FROM customers c LEFT JOIN customer_addr ca ON ca.cid=c.id WHERE c.name='$NAME_TO_DELETE');
DELETE FROM customer_addr WHERE cid = (SELECT id FROM customers WHERE name='$NAME_TO_DELETE');
If you have the customer ID already (EDIT: You do), you can skip most of that:
DELETE FROM addresses WHERE id IN (SELECT aid FROM customer_addr WHERE cid=$TARGET_CID);
DELETE FROM customer_addr WHERE cid = $TARGET_CID;
Wrap those with the appropriate transactional BEGIN/END, to make sure that you don't end up in an inconsistent state, and you should be set.