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Unleasing the power with Subqueries
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‎SQL Subqueries and Temporary Tables/Lesson 4 - SQL Subqueries and Temporary Tables.sql‎

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/*
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Find the average number of events for each day for each channel.
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*/
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SELECT channel,
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AVG(num_events) avg_num_events
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FROM (
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SELECT channel,
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DATE_TRUNC('day', occurred_at),
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COUNT(*) num_events
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FROM web_events
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GROUP BY 1, 2
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) sub_table
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GROUP BY channel;
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/*
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Use DATE_TRUNC to pull "month" level information about the first order
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ever placed in the orders table. Use this result to find only the orders
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that took place in the same month-year combo as the first order and then
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pull the average for each type of paper 'qty' in this month and the total
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amount spent on all orders.
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*/
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SELECT AVG(standard_qty) standard,
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AVG(gloss_qty) gloss,
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AVG(poster_qty) poster,
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SUM(total_amt_usd)
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FROM orders
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WHERE DATE_TRUNC('month', occurred_at) =
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(SELECT MIN(DATE_TRUNC('month', occurred_at))
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FROM orders)
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/*
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Provide the name of the sales_rep in each region with the largest amount
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of total_amt_usd sales.
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*/
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SELECT sub2.region,
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sub1.sales_rep,
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sub2.total_amt_usd
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FROM (
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SELECT r.name region,
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s.name sales_rep,
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SUM(o.total_amt_usd) total_amt_usd
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FROM orders o
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JOIN accounts a
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ON a.id = o.account_id
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JOIN sales_reps s
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ON s.id = a.sales_rep_id
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JOIN region r
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ON r.id = s.region_id
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GROUP BY 1, 2
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) sub1
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JOIN (
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SELECT region,
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MAX(total_amt_usd) total_amt_usd
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FROM (
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SELECT r.name region,
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s.name sales_rep,
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SUM(o.total_amt_usd) total_amt_usd
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FROM orders o
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JOIN accounts a
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ON a.id = o.account_id
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JOIN sales_reps s
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ON s.id = a.sales_rep_id
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JOIN region r
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ON r.id = s.region_id
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GROUP BY 1, 2
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) sub
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GROUP BY 1
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) sub2
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ON sub1.region = sub2.region
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AND sub1.total_amt_usd = sub2.total_amt_usd
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ORDER BY 3;
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/*
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For the region with the largest (sum) of sales total_amt_usd, how many
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total (count) orders were placed?
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*/
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SELECT r.name region,
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SUM(o.total_amt_usd) total_amt_usd,
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COUNT(*)
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FROM orders o
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JOIN accounts a
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ON a.id = o.account_id
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JOIN sales_reps s
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ON s.id = a.sales_rep_id
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JOIN region r
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ON r.id = s.region_id
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GROUP BY 1
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ORDER BY 2 DESC
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LIMIT 1;
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/*
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For the name of the account that purchased the most (in total over their
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lifetime as a customer) standard_qty paper, how many accounts still had
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more in total purchases?
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*/
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SELECT COUNT(*)
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FROM (
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SELECT a.name, SUM(o.total)
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FROM accounts a
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JOIN orders o
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ON o.account_id = a.id
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GROUP BY a.name
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HAVING SUM(o.total) > (
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SELECT total
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FROM (
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SELECT SUM(o.standard_qty) standard_qty,
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SUM(o.total) total
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FROM orders o
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GROUP BY account_id
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ORDER BY 1 DESC
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LIMIT 1
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)sub1
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)
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)sub;
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/*
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For the customer that spent the most (in total over their lifetime as a
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customer) total_amt_usd, how many web_events did they have for each
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channel?
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*/
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SELECT channel,
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w.account_id,
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COUNT(*)
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FROM web_events w
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JOIN (
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SELECT o.account_id, SUM(o.total_amt_usd)
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FROM orders o
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GROUP BY 1
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ORDER BY 2 DESC
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LIMIT 1
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) sub
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ON sub.account_id = w.account_id
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GROUP BY 1, 2
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ORDER BY 3 DESC;
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/*
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What is the lifetime average amount spent in terms of total_amt_usd for
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the top 10 total spending accounts?
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*/
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SELECT AVG(total)
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FROM (
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SELECT account_id,
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SUM(total_amt_usd) total
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FROM orders
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GROUP BY 1
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ORDER BY 2 DESC
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LIMIT 10
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) sub;
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/*
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What is the lifetime average amount spent in terms of total_amt_usd for
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only the companies that spent more than the average of all orders.
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*/
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SELECT AVG(total_amt_usd)
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FROM (
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SELECT account_id,
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AVG(total_amt_usd) total_amt_usd
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FROM orders
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GROUP BY account_id
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) sub
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WHERE total_amt_usd >
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(SELECT AVG(total_amt_usd) total_amt_usd
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FROM orders)
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/*
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Provide the name of the sales_rep in each region with the largest amount
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of total_amt_usd sales.
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*/
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WITH
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sub1 AS (
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SELECT r.name region,
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s.name sales_rep,
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SUM(o.total_amt_usd) total_amt_usd
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FROM orders o
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JOIN accounts a
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ON a.id = o.account_id
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JOIN sales_reps s
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ON s.id = a.sales_rep_id
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JOIN region r
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ON r.id = s.region_id
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GROUP BY 1, 2
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),
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sub2 AS (
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SELECT region,
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MAX(total_amt_usd) total_amt_usd
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FROM sub1
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GROUP BY 1
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)
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SELECT sub2.region,
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sub1.sales_rep,
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sub2.total_amt_usd
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FROM sub1
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JOIN sub2
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ON sub1.region = sub2.region
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AND sub1.total_amt_usd = sub2.total_amt_usd
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ORDER BY 3;
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/*
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For the region with the largest (sum) of sales total_amt_usd, how many
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total (count) orders were placed?
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*/
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SELECT r.name region,
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SUM(o.total_amt_usd) total_amt_usd,
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COUNT(*)
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FROM orders o
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JOIN accounts a
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ON a.id = o.account_id
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JOIN sales_reps s
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ON s.id = a.sales_rep_id
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JOIN region r
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ON r.id = s.region_id
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GROUP BY 1
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ORDER BY 2 DESC
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LIMIT 1;
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/*
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For the name of the account that purchased the most (in total over their
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lifetime as a customer) standard_qty paper, how many accounts still had
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more in total purchases?
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*/
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WITH
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sub1 AS (
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SELECT SUM(o.standard_qty) standard_qty,
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SUM(o.total) total
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FROM orders o
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GROUP BY account_id
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ORDER BY 1 DESC
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LIMIT 1
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),
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sub2 AS (
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SELECT a.name, SUM(o.total)
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FROM accounts a
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JOIN orders o
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ON o.account_id = a.id
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GROUP BY a.name
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HAVING SUM(o.total) > (SELECT total FROM sub1)
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)
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SELECT COUNT(*)
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FROM sub2;
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/*
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For the customer that spent the most (in total over their lifetime as a
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customer) total_amt_usd, how many web_events did they have for each
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channel?
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*/
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WITH
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sub AS (
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SELECT o.account_id, SUM(o.total_amt_usd)
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FROM orders o
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GROUP BY 1
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ORDER BY 2 DESC
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LIMIT 1
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)
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SELECT channel,
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w.account_id,
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COUNT(*)
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FROM web_events w
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JOIN sub
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ON sub.account_id = w.account_id
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GROUP BY 1, 2
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ORDER BY 3 DESC;
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/*
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What is the lifetime average amount spent in terms of total_amt_usd
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for the top 10 total spending accounts?
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*/
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WITH
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sub AS (
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SELECT account_id,
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SUM(total_amt_usd) total
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FROM orders
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GROUP BY 1
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ORDER BY 2 DESC
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LIMIT 10
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)
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SELECT AVG(total)
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FROM sub;
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/*
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What is the lifetime average amount spent in terms of total_amt_usd
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for only the companies that spent more than the average of all orders.
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*/
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WITH
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sub AS (
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SELECT account_id,
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AVG(total_amt_usd) total_amt_usd
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FROM orders
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GROUP BY account_id
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)
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SELECT AVG(total_amt_usd)
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FROM sub
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WHERE total_amt_usd >
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(SELECT AVG(total_amt_usd) total_amt_usd
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FROM orders)
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