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PQ #1

I have a query that starts with the line:

SELECT books.isbn, order_lines.isbn

...why would I want to see isbns from two different tables? What sort of query would warrant that - an inner join or an outer join?

Assume the table "books" contains books that the company stocks. Assume the table order_lines only contains books that have actually been ordered.

Solution Preview

1) You want to use inner join on tables 'books' and 'order_lines'
when you want to get all records from both of tables 'books' and 'order_lines'
where there is a match i.e having same ISBN. If there are rows in 'books' that do not have matches in 'order_lines', those rows (BOOKS records) will not be listed.
So innerjoin will give all the books records that are in both tables 'books' and 'order_lines'
So with the assumption the table "books" contains books that the company stocks. Assume the table order_lines only contains books that have actually been ordered.
the innerjoin query results displaying companystocks books that have been ...

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