SQL Exercises: Largest and smallest orders are produced on each date
SQL UNION: Exercise-4 with Solution
4. From the following table, write a SQL query to find the salespersons who generated the largest and smallest orders on each date. Return salesperson ID, name, order no., highest on/lowest on, order date.
Sample table: Salesman
Sample table: Orders
SELECT a.salesman_id, name, ord_no, 'highest on', ord_date FROM salesman a, orders b WHERE a.salesman_id =b.salesman_id AND b.purch_amt= (SELECT MAX (purch_amt) FROM orders c WHERE c.ord_date = b.ord_date) UNION (SELECT a.salesman_id, name, ord_no, 'lowest on', ord_date FROM salesman a, orders b WHERE a.salesman_id =b.salesman_id AND b.purch_amt= (SELECT MIN (purch_amt) FROM orders c WHERE c.ord_date = b.ord_date))
salesman_id name ord_no ?column? ord_date 5001 James Hoog 70002 lowest on 2012-10-05 5001 James Hoog 70005 highest on 2012-07-27 5001 James Hoog 70005 lowest on 2012-07-27 5001 James Hoog 70008 highest on 2012-09-10 5001 James Hoog 70013 highest on 2012-04-25 5001 James Hoog 70013 lowest on 2012-04-25 5002 Nail Knite 70001 highest on 2012-10-05 5002 Nail Knite 70012 highest on 2012-06-27 5002 Nail Knite 70012 lowest on 2012-06-27 5003 Lauson Hen 70003 highest on 2012-10-10 5003 Lauson Hen 70004 highest on 2012-08-17 5005 Pit Alex 70009 lowest on 2012-09-10 5006 Mc Lyon 70010 lowest on 2012-10-10 5007 Paul Adam 70011 lowest on 2012-08-17
The said query in SQL that selects the salesman_id, name, ord_no, and ord_date for each order where the purchase amount is the highest or lowest for that order date. The query uses a subquery to find the highest or lowest purchase amount for each order date, and then joins the orders and salesman tables using the salesman_id column.
The output of the query will consist of two sets of rows: one for the highest purchase amount and one for the lowest purchase amount for each order date. The 'highest on' and 'lowest on' values are added as literals to indicate which one of the two values it is displaying.
The outer query of the first subquery selects the rows where the purchase amount matches the maximum value.
This UNION keyword combines the results of the first query with the results of the second query.
The outer query of the second subquery selects the rows where the purchase amount matches the minimum value.
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Previous SQL Exercise: Salesmen, customer involved in inventory management.
Next SQL Exercise: Largest and smallest orders on each date.
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SQL: Tips of the Day
Grouped LIMIT in PostgreSQL: Show the first N rows for each group?
db=# SELECT * FROM xxx; id | section_id | name ----+------------+------ 1 | 1 | A 2 | 1 | B 3 | 1 | C 4 | 1 | D 5 | 2 | E 6 | 2 | F 7 | 3 | G 8 | 2 | H (8 rows)
I need the first 2 rows (ordered by name) for each section_id, i.e. a result similar to:
id | section_id | name ----+------------+------ 1 | 1 | A 2 | 1 | B 5 | 2 | E 6 | 2 | F 7 | 3 | G (5 rows)
PostgreSQL v9.3 you can do a lateral join
select distinct t_outer.section_id, t_top.id, t_top.name from t t_outer join lateral ( select * from t t_inner where t_inner.section_id = t_outer.section_id order by t_inner.name limit 2 ) t_top on true order by t_outer.section_id;
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