added solutions & demo queries

demo-queries-from slides-01.sql

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+SELECT invoice_number, invoice_date, invoice_total
+FROM invoices
+WHERE invoice_total > 
+    (SELECT AVG(invoice_total)
+     FROM invoices)
+ORDER BY invoice_total;

demo-queries-from slides-02.sql

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+SELECT invoice_number, invoice_date, invoice_total
+FROM invoices JOIN vendors
+    ON invoices.vendor_id = vendors.vendor_id
+WHERE vendor_state = 'CA'
+ORDER BY invoice_date;
+
+SELECT invoice_number, invoice_date, invoice_total
+FROM invoices
+WHERE vendor_id IN
+    (SELECT vendor_id
+     FROM vendors
+     WHERE vendor_state = 'CA')
+ORDER BY invoice_date;

demo-queries-from slides-03.sql

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+SELECT vendor_id, vendor_name, vendor_state
+FROM vendors
+WHERE vendor_id NOT IN
+    (SELECT DISTINCT vendor_id
+     FROM invoices)
+ORDER BY vendor_id;
+
+SELECT v.vendor_id, vendor_name, vendor_state
+FROM vendors v LEFT JOIN invoices i
+    ON v.vendor_id = i.vendor_id
+WHERE i.vendor_id IS NULL
+ORDER BY v.vendor_id;

demo-queries-from slides-04.sql

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+SELECT invoice_number, invoice_date, 
+    invoice_total - payment_total - credit_total AS balance_due
+FROM invoices
+WHERE invoice_total - payment_total - credit_total  > 0 
+  AND invoice_total - payment_total - credit_total <
+    (
+     SELECT AVG(invoice_total - payment_total - credit_total)
+     FROM invoices
+     WHERE invoice_total - payment_total - credit_total > 0
+    )
+ORDER BY invoice_total DESC;

demo-queries-from slides-05.sql

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+SELECT vendor_name, invoice_number, invoice_total
+FROM invoices i JOIN vendors v ON i.vendor_id = v.vendor_id
+WHERE invoice_total > ALL
+    (SELECT invoice_total
+     FROM invoices
+     WHERE vendor_id = 34)
+ORDER BY vendor_name;

demo-queries-from slides-06.sql

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+SELECT vendor_name, invoice_number, invoice_total
+FROM vendors JOIN invoices ON vendors.vendor_id = invoices.vendor_id
+WHERE invoice_total < ANY
+    (SELECT invoice_total
+     FROM invoices
+     WHERE vendor_id = 115);

demo-queries-from slides-07.sql

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+SELECT vendor_id, invoice_number, invoice_total
+FROM invoices i
+WHERE invoice_total >
+    (SELECT AVG(invoice_total)
+     FROM invoices
+     WHERE vendor_id = i.vendor_id)
+ORDER BY vendor_id, invoice_total;

demo-queries-from slides-08.sql

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+SELECT vendor_id, vendor_name, vendor_state
+FROM vendors
+WHERE NOT EXISTS
+    (SELECT * 
+     FROM invoices
+     WHERE vendor_id = vendors.vendor_id);

demo-queries-from slides-09.sql

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+SELECT vendor_name,
+    (SELECT MAX(invoice_date) FROM invoices
+     WHERE vendor_id = vendors.vendor_id) AS latest_inv
+FROM vendors
+ORDER BY latest_inv DESC;
+
+SELECT vendor_name, MAX(invoice_date) AS latest_inv
+FROM vendors v 
+    LEFT JOIN invoices i ON v.vendor_id = i.vendor_id
+GROUP BY vendor_name
+ORDER BY latest_inv DESC;

demo-queries-from slides-10.sql

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+SELECT vendor_state, MAX(sum_of_invoices) AS max_sum_of_invoices
+FROM
+(
+     SELECT vendor_state, vendor_name,
+         SUM(invoice_total) AS sum_of_invoices
+     FROM vendors v JOIN invoices i 
+         ON v.vendor_id = i.vendor_id
+     GROUP BY vendor_state, vendor_name
+) t
+GROUP BY vendor_state
+ORDER BY vendor_state;

demo-queries-from slides-11.sql

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+SELECT t1.vendor_state, vendor_name, t1.sum_of_invoices
+FROM
+    (
+        -- invoice totals by vendor
+        SELECT vendor_state, vendor_name,
+            SUM(invoice_total) AS sum_of_invoices
+        FROM vendors v JOIN invoices i 
+            ON v.vendor_id = i.vendor_id
+        GROUP BY vendor_state, vendor_name
+    ) t1
+    JOIN
+        (
+            -- top invoice totals by state
+            SELECT vendor_state,  
+                   MAX(sum_of_invoices) AS sum_of_invoices
+            FROM
+            (
+                 -- invoice totals by vendor
+                 SELECT vendor_state, vendor_name,
+                     SUM(invoice_total) AS sum_of_invoices
+                 FROM vendors v JOIN invoices i 
+                     ON v.vendor_id = i.vendor_id
+                 GROUP BY vendor_state, vendor_name
+            ) t2
+            GROUP BY vendor_state
+        ) t3
+    ON t1.vendor_state = t3.vendor_state AND 
+       t1.sum_of_invoices = t3.sum_of_invoices
+ORDER BY vendor_state;

demo-queries-from slides-12.sql

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+SELECT vendor_state, vendor_name, SUM(invoice_total) AS sum_of_invoices
+FROM vendors v JOIN invoices i 
+    ON v.vendor_id = i.vendor_id
+GROUP BY vendor_state, vendor_name;
+
+SELECT vendor_state, MAX(sum_of_invoices) AS sum_of_invoices
+FROM
+(
+     SELECT vendor_state, vendor_name,
+         SUM(invoice_total) AS sum_of_invoices
+     FROM vendors v JOIN invoices i 
+         ON v.vendor_id = i.vendor_id
+     GROUP BY vendor_state, vendor_name
+) t
+GROUP BY vendor_state;

exercise-01.sql

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+SELECT vendor_name
+FROM vendors
+WHERE vendor_id IN
+     (SELECT DISTINCT vendor_id FROM invoices)
+ORDER BY vendor_name

exercise-02.sql

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+SELECT invoice_number, invoice_total
+FROM invoices
+WHERE payment_total >
+     (SELECT AVG(payment_total)
+      FROM invoices
+      WHERE payment_total > 0)
+ORDER BY invoice_total DESC

exercise-03.sql

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+SELECT account_number, account_description
+FROM general_ledger_accounts gl
+WHERE NOT EXISTS
+    (SELECT *
+     FROM invoice_line_items
+     WHERE account_number = gl.account_number)
+ORDER BY account_number

exercise-04.sql

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+SELECT vendor_name, i.invoice_id, invoice_sequence, line_item_amount
+FROM vendors v JOIN invoices i
+  ON v.vendor_id = i.vendor_id
+JOIN invoice_line_items li
+  ON i.invoice_id = li.invoice_id
+WHERE i.invoice_id IN
+      (SELECT DISTINCT invoice_id
+       FROM invoice_line_items               
+       WHERE invoice_sequence > 1)
+ORDER BY vendor_name, i.invoice_id, invoice_sequence

exercise-05.sql

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+SELECT SUM(invoice_max) AS sum_of_maximums
+FROM (SELECT vendor_id, MAX(invoice_total) AS invoice_max
+      FROM invoices
+      WHERE invoice_total - credit_total - payment_total > 0
+      GROUP BY vendor_id) t

exercise-06.sql

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+SELECT vendor_name, vendor_city, vendor_state
+FROM vendors
+WHERE CONCAT(vendor_state, vendor_city) NOT IN 
+    (SELECT CONCAT(vendor_state, vendor_city) as vendor_city_state
+     FROM vendors
+     GROUP BY vendor_city_state
+     HAVING COUNT(*) > 1)
+ORDER BY vendor_state, vendor_city

exercise-07.sql

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+SELECT vendor_name, invoice_number,
+       invoice_date, invoice_total
+FROM invoices i JOIN vendors v
+  ON i.vendor_id = v.vendor_id
+WHERE invoice_date =
+  (SELECT MIN(invoice_date)
+   FROM invoices 
+   WHERE vendor_id = i.vendor_id)
+ORDER BY vendor_name

exercise-08.sql

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+SELECT vendor_name, invoice_number,
+       invoice_date, invoice_total
+FROM invoices i
+    JOIN
+    (
+      SELECT vendor_id, MIN(invoice_date) AS oldest_invoice_date
+      FROM invoices
+      GROUP BY vendor_id
+    ) oi
+    ON i.vendor_id = oi.vendor_id AND
+       i.invoice_date = oi.oldest_invoice_date
+    JOIN vendors v
+    ON i.vendor_id = v.vendor_id
+ORDER BY vendor_name