loading..
Ðóññêèé    English
23:27
go

Exercise #56 (tips and solutions)

Below is a solution which accounts the sunken ships correctly. This solution has an insignificant mistake; we suggest you to find it by yourself. In case of difficulty, return to solution 3.12.3.

Console
Execute
  1. SELECT class, SUM(r) sunks 
  2. FROM (SELECT name, class, CASE 
  3.                              WHEN result = 'sunk' 
  4.                              THEN 1 ELSE 0 
  5.                           END r 
  6.       FROM Ships AS s LEFT JOIN 
  7.            Outcomes AS o ON o.ship = s.name 
  8.       UNION 
  9.       SELECT ship, class, CASE 
  10.                              WHEN result = 'sunk' 
  11.                              THEN 1 ELSE 0 
  12.                           END r 
  13.       FROM Classes c JOIN 
  14.            (SELECT * 
  15.             FROM Outcomes
  16.             WHERE NOT Ship IN (SELECT name 
  17.                                FROM Ships)
  18.                                ) AS ot ON ot.ship = c.class
  19.             ) AS b GROUP BY class;

To return to discussion of exercise #56

To solve a problem on SQL-EX.RU
Bookmark and Share
Tags
aggregate functions Airport ALL AND AS keyword ASCII AVG Battles Bezhaev Bismarck C.J.Date calculated columns Cartesian product CASE cast CHAR CHARINDEX Chebykin check constraint classes COALESCE common table expressions comparison predicates Computer firm CONVERT correlated subqueries COUNT CROSS APPLY CTE data type conversion data types database schema date/time functions DATEADD DATEDIFF DATENAME DATEPART DATETIME DDL DEFAULT DEFAULT VALUES DELETE DISTINCT DML duplicates EXCEPT exercise (-2) exercise 19 exercise 23 exercise 32 More tags
The book was updated
several days ago
©SQL-EX,2008 [Evolution] [Feedback] [About] [Links] [Team]
All right reserved.
Rambler's Top100