Assignment2-SQL

02_activities/assignments/assignment2.sql

@@ -19,8 +19,14 @@ HINT: keep the syntax the same, but edited the correct components with the strin
 The `||` values concatenate the columns into strings. 
 Edit the appropriate columns -- you're making two edits -- and the NULL rows will be fixed. 
 All the other rows will remain the same.) */
-
-
+SELECT
+  product_name
+  || ', '
+  || COALESCE(product_size, '')
+  || ' ('
+  || COALESCE(product_qty_type, 'unit')
+  || ')'
+FROM product;
 
 --Windowed Functions
 /* 1. Write a query that selects from the customer_purchases table and numbers each customer’s  
@@ -32,18 +38,87 @@ each new market date for each customer, or select only the unique market dates p
 (without purchase details) and number those visits. 
 HINT: One of these approaches uses ROW_NUMBER() and one uses DENSE_RANK(). */
 
+--dense_rank
+SELECT
+  customer_id,
+  market_date,
+  DENSE_RANK() 
+    OVER (
+      PARTITION BY customer_id 
+      ORDER BY market_date
+    ) AS visit_number
+FROM (
+  SELECT DISTINCT
+    customer_id,
+    market_date
+  FROM customer_purchases
+) AS unique_visits;
+
+--row_number
+SELECT
+  customer_id,
+  market_date,
+  ROW_NUMBER() 
+    OVER (
+      PARTITION BY customer_id 
+      ORDER BY market_date
+    ) AS visit_number
+FROM customer_purchases;
 
 
 /* 2. Reverse the numbering of the query from a part so each customer’s most recent visit is labeled 1, 
 then write another query that uses this one as a subquery (or temp table) and filters the results to 
 only the customer’s most recent visit. */
-
-
+--Reverse-rank
+SELECT
+  customer_id,
+  market_date,
+  DENSE_RANK() 
+    OVER (
+      PARTITION BY customer_id
+      ORDER BY market_date DESC
+    ) AS recent_visit_rank
+FROM (
+  SELECT DISTINCT
+    customer_id,
+    market_date
+  FROM customer_purchases
+) AS unique_visits;
+
+--filter recent visit
+WITH ranked_visits AS (
+  SELECT
+    customer_id,
+    market_date,
+    DENSE_RANK() 
+      OVER (
+        PARTITION BY customer_id
+        ORDER BY market_date DESC
+      ) AS recent_visit_rank
+  FROM (
+    SELECT DISTINCT
+      customer_id,
+      market_date
+    FROM customer_purchases
+  ) AS unique_visits
+)
+SELECT
+  customer_id,
+  market_date       
+FROM ranked_visits
+WHERE recent_visit_rank = 1;
 
 /* 3. Using a COUNT() window function, include a value along with each row of the 
 customer_purchases table that indicates how many different times that customer has purchased that product_id. */
 
-
+SELECT
+  cp.*,
+  COUNT(*) 
+    OVER (
+      PARTITION BY customer_id,
+                   product_id
+    ) AS times_purchased
+FROM customer_purchases AS cp;
 
 -- String manipulations
 /* 1. Some product names in the product table have descriptions like "Jar" or "Organic". 
@@ -57,10 +132,27 @@ Remove any trailing or leading whitespaces. Don't just use a case statement for
 
 Hint: you might need to use INSTR(product_name,'-') to find the hyphens. INSTR will help split the column. */
 
+SELECT
+  product_name,
+  CASE 
+    WHEN INSTR(product_name, '-') > 0
+    THEN TRIM(
+           SUBSTR(
+             product_name,
+             INSTR(product_name, '-') + 1
+           )
+         )
+    ELSE NULL
+  END AS description
+FROM product;
 
 
 /* 2. Filter the query to show any product_size value that contain a number with REGEXP. */
-
+SELECT
+  product_name,
+  product_size
+FROM product
+WHERE product_size REGEXP '[0-9]';
 
 
 -- UNION
@@ -73,7 +165,32 @@ HINT: There are a possibly a few ways to do this query, but if you're struggling
 3) Query the second temp table twice, once for the best day, once for the worst day, 
 with a UNION binding them. */
 
-
+WITH daily_totals AS (
+  SELECT
+    market_date,
+    SUM(quantity * cost_to_customer_per_qty) AS total_sales
+  FROM customer_purchases
+  GROUP BY market_date
+)
+SELECT
+  'Highest'    AS which,
+  market_date,
+  total_sales
+FROM daily_totals
+WHERE total_sales = (
+  SELECT MAX(total_sales) 
+  FROM daily_totals
+)
+UNION
+SELECT
+  'Lowest'     AS which,
+  market_date,
+  total_sales
+FROM daily_totals
+WHERE total_sales = (
+  SELECT MIN(total_sales) 
+  FROM daily_totals
+);
 
 
 /* SECTION 3 */
@@ -88,28 +205,62 @@ Remember, CROSS JOIN will explode your table rows, so CROSS JOIN should likely b
 Think a bit about the row counts: how many distinct vendors, product names are there (x)?
 How many customers are there (y). 
 Before your final group by you should have the product of those two queries (x*y).  */
-
+SELECT
+  v.vendor_name,
+  p.product_name,
+  SUM(5 * vi.original_price) AS potential_revenue
+FROM vendor_inventory AS vi
+JOIN vendor   AS v ON vi.vendor_id   = v.vendor_id
+JOIN product  AS p ON vi.product_id  = p.product_id
+CROSS JOIN customer AS c
+GROUP BY
+  v.vendor_name,
+  p.product_name;
 
 
 -- INSERT
 /*1.  Create a new table "product_units". 
 This table will contain only products where the `product_qty_type = 'unit'`. 
 It should use all of the columns from the product table, as well as a new column for the `CURRENT_TIMESTAMP`.  
 Name the timestamp column `snapshot_timestamp`. */
-
+CREATE TABLE product_units AS
+SELECT
+  *,
+  CURRENT_TIMESTAMP AS snapshot_timestamp
+FROM product
+WHERE product_qty_type = 'unit';
 
 
 /*2. Using `INSERT`, add a new row to the product_units table (with an updated timestamp). 
 This can be any product you desire (e.g. add another record for Apple Pie). */
 
-
+INSERT INTO product_units (
+  product_id,
+  product_name,
+  product_size,
+  product_qty_type,
+  snapshot_timestamp
+)
+VALUES (
+  999,                       
+  'Apple Pie',               
+  'Individual',             
+  'unit',                   
+  CURRENT_TIMESTAMP          
+);
 
 -- DELETE
 /* 1. Delete the older record for the whatever product you added. 
 
 HINT: If you don't specify a WHERE clause, you are going to have a bad time.*/
 
-
+DELETE FROM product_units
+WHERE product_name = 'Apple Pie'
+  AND snapshot_timestamp < (
+    SELECT MAX(snapshot_timestamp)
+    FROM product_units
+    WHERE product_name = 'Apple Pie'
+);
 
 -- UPDATE
 /* 1.We want to add the current_quantity to the product_units table. 
@@ -129,5 +280,20 @@ Finally, make sure you have a WHERE statement to update the right row,
 When you have all of these components, you can run the update statement. */
 
 
+ALTER TABLE product_units
+ADD current_quantity INT;
+
+
+UPDATE product_units AS pu
+SET current_quantity = COALESCE(
+  (
+    SELECT vi.quantity
+    FROM vendor_inventory AS vi
+    WHERE vi.product_id = pu.product_id
+    ORDER BY vi.market_date DESC
+    LIMIT 1
+  ),
+  0
+);