I have that database diagram (MySQL). Each Book has assigned a BookLanguage. Each BookLanguage has two different LanguageNames (the globalization purpose). And also, each Book can have an additional BookLanguage (but it's not required).
And here's the problem - I'm stuck here while building a SQL query for searching for that Books, whose have some string in the BookLanguageNames. It's simple to build the query with joining the BookLanguage and BookLanguageNames but how to cope with the AdditionalBookLanguages ?

Codecolumn in theBookLanguagetable? Is it necessary? Why is not in theBookLanguageNamesorAdditionalBookLanguages?