一个简单的选择SQL语句

Question

我正在使用sql server 2008 R2，我有表：

Book: id, name, ...  >> 3500 rows
BookChapter: id, bookid, content(nvarchar(max)... >> it has about 300000 rows

2之间没有关系。

现在我想要计算目前没有章节的所有书籍。

SELECT     COUNT(Id) AS Expr1
FROM         dbo.Book
WHERE     (Id NOT IN  (SELECT BookId FROM dbo.BookChapter))   

总是让超时过期。我怎样才能实现它？

Answer 1

尝试使用左连接类似于不存在但有时表现更好。

select count(1) as Counts
from 
    dbo.Book B
    left join dbo.BookChapter BC on BC.BookID = B.ID
where
    BC.BookID is null

Answer 2

你的子查询变得非常大。您可以尝试通过BookId对其进行分组。

SELECT COUNT(Id) AS Expr1
FROM   dbo.Book
WHERE  (Id NOT IN  (SELECT BookId FROM dbo.BookChapter GROUP BY BookId)) 

使用NOT EXISTS;

的另一个选项

SELECT COUNT(B.Id) AS count
FROM   dbo.Book B
WHERE  NOT EXISTS (SELECT * FROM dbo.BookChapter WHERE BookId=B.BookId))

Answer 3

不要使用“不在”。这太慢了。根据apartidge的第二个建议你可以使用“not exists”，或者你可以做一些完全不直观的事情：

select count(*) BooksWithoutChapters
from book
where id in 
(select id
from book
minus 
select bookid
from BookChapter
)