Posted by Miks on 10/01/07 11:42

The database scheme consists of four relations:

Product(maker, model, type)
PC(code, model, speed, ram, hd, cd, price)
Laptop(code, model, speed, ram, hd, screen, price)
Printer(code, model, color, type, price)

The relation "Product" shows the maker, model number, and type (pc,
laptop, or printer). It is assumed that model numbers are unique for
all the makers and product types. For each model number specifying pc
in the relation "PC", its listed speed (of the processor in MGz), total
RAM (in MGb), hd capacity (in Gb), CD ROM speed (for example, '4x'),
and the price. The relation "Laptop" is similar to that one of PCs
except for the CD ROM speed which is replaced by screen size (in
inches). For each printer model in the relation "Printer" it is pointed
whether the printer is color or not (color attribute is 'y' for color
printers; otherwise it is 'n'), printer type (laser, jet, or matrix),
and the price.

I need to write a query for Find printer makers.
Result set: maker.

My Query is

select distinct product.maker from product inner join printer on
product.model = printer.model


I get the message
Your query produced correct result set on main database, but it failed
test on second, checking database.
* Wrong number of records (less by 1)

This question is an SQL exercise in URL http://www.sql-ex.ru/

Can anyobe explain me "correct result set on main database," why "but
it failed test on second, checking database."
* Wrong number of records (less by 1)

Thank you very much,

Miks

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