解决方案

1. SELECT a.primary_poc, w.occurred_at, w.channel, a.name
   FROM web_events w
   JOIN accounts a
   ON w.account_id = a.id
   WHERE a.name = 'Walmart';

2.

SELECT r.name region, s.name rep, a.name account
FROM sales_reps s
JOIN region r
ON s.region_id = r.id
JOIN accounts a
ON a.sales_rep_id = s.id
ORDER BY a.name;

3. SELECT r.name region, a.name account,
   o.total_amt_usd/(o.total + 0.01) unit_price
   FROM region r
   JOIN sales_reps s
   ON s.region_id = r.id
   JOIN accounts a
   ON a.sales_rep_id = s.id
   JOIN orders o
   ON o.account_id = a.id;