SQL查询和字符串搜索

Question

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 ?

Answer 1

How about simplifying the database design? Have three tables Book , BookLanguageName (both of them similar structure to yours) and, instead of AdditionalBookLanguage and BookLanguage have a "lookup table" - BookLanguage :

1. Book - here you keep all the information about the books.
2. BookLanguage - only three columns: BookID, BookLanguageID (or Code) and a boolean is_additional. BookID and BookLanguageID would be a composite primary key.
3. Language - here you keep all information related to a particular language.

In such case, writing query would be easier.