Combining multiple queries - sql

Question

I want a table with all customers and their last charge transaction date and their last invoice date. I have the first two, but don't know how to add the last invoice date to the table. Here's what I have so far:
WITH
--Last customer transaction
cust_trans AS (
SELECT customer_id, created
FROM charges a
WHERE created = (
SELECT MAX(created) AS last_trans
FROM charges b
WHERE a.customer_id = b.customer_id)),
--All customers
all_cust AS (
SELECT customers.id AS customer, customers.email, CAST(customers.created AS DATE) AS join_date, ((1.0 * customers.account_balance)/100) AS balance
FROM customers),
--Last customer invoice
cust_inv AS (
SELECT customer_id, date
FROM invoices a
WHERE date = (
SELECT MAX(date) AS last_inv
FROM invoices b
WHERE a.customer_id = b.customer_id))
SELECT * FROM cust_trans
RIGHT JOIN all_cust ON all_cust.customer = cust_trans.customer_id
ORDER BY join_date;

Answer 1

This should get what you need. Notice each individual subquery is left-joined to the customer table, so you always START with the customer, and IF there is a corresponding record in each subquery for max charge date or max invoice date, it will be pulled in. Now, you may want to apply a COALESCE() for the max dates to prevent showing nulls, such as
COALESCE(maxCharges.LastChargeDate, '') AS LastChargeDate
but your call.
SELECT
c.id AS customer,
c.email,
CAST(c.created AS DATE) AS join_date,
((1.0 * c.account_balance) / 100) AS balance,
maxCharges.LastChargeDate,
maxInvoices.LastInvoiceDate
FROM
customers c
LEFT JOIN
(SELECT
customer_id,
MAX(created) LastChargeDate
FROM
charges
GROUP BY
customer_id) maxCharges ON c.id = maxCharges.customer_id
LEFT JOIN
(SELECT
customer_id,
MAX(date) LastInvoiceDate
FROM
invoices
GROUP BY
customer_id) maxInvoices ON c.id = maxInvoices.customer_id
ORDER BY
c.created