SQL Server 查询允许我显示书柜中的书籍概览

Question

我正在尝试让我的程序显示数据库中所有书架的概览，以及相关的书架/隔间以及这些书架或隔间中的书籍。

我正在使用 Microsoft Visual Studio 2017 Windows 窗体应用程序。

我的SQL Server数据库结构如下：

• user 表（用户 ID、用户名、密码）
• bookcase table (bookcaseId, name, location, userId)
• Shelf table (shelfId, bookcaseId)
• compartment table (compartmentId, bookcaseId)
• book table（bookid、title、author、serie、genre、compartmentId、shelfId）

我知道如何通过使用每个表中的Select * 来使用查询来获取所有书籍、书架、用户等的概览。

我也知道订购时我只需使用Order by bookcaseId。

我将如何实现这一目标？

Answer 1

另一种可能的方法是将bookshelves 用于您的FROM 子句。这种方法的原因（如果我正确理解您的数据库设计）是事实，bookcaseId 似乎是shelf 和compartment 表中的外键。

SELECT 
    bk.bookcaseId, bk.name, bk.location,
    b.bookid, b.title, b.author, b.serie, b.genre, b.compartmentId, b.shelfId
FROM bookcase bk
LEFT JOIN shelf s ON (bk.bookcaseId = s.bookcaseId)
LEFT JOIN compartment c ON (bk.bookcaseId = c.bookcaseId)
LEFT JOIN book b ON (c.compartmentId = b.compartmentId) AND (s.shelfId = b.shelfId)
ORDER BY bk.bookcaseId, s.shelfId, c.compartmentId

Answer 2

您可以使用正确的键加入它们。
然后从他们那里获取您需要的字段。

那个 bookcaseId 是两个表中的外键。

因此，可能在 books 表中填充了隔间 ID 或/和架子 ID。

但您可以同时加入两者，然后同时获得两者的用户。

SELECT 
book.title AS book_title, 
book.author AS book_author, 
book.serie AS book_serie,
book.genre AS book_genre,
bcs.name AS shelf_bookcase_name, 
bcs.location AS shelf_bookcase_location,
us.username AS shelf_bc_username,
bcc.name AS compartment_bookcase_name, 
bcc.location AS compartment_bookcase_location,
uc.username AS compartment_bc_username
FROM book
LEFT JOIN compartment AS cmp ON cmp.compartmentId = book.compartmentId
LEFT JOIN bookcase AS bcc ON bcc.bookcaseId = cmp.bookcaseId
LEFT JOIN [user] AS uc ON uc.userId = bcc.userId
LEFT JOIN shelf ON shelf.shelfId = book.shelfId
LEFT JOIN bookcase AS bcs ON bcs.bookcaseId = shelf.bookcaseId
LEFT JOIN [user] AS us ON us.userId = bcs.userId
ORDER BY coalesce(shelf.bookcaseId, cmp.bookcaseId)