Question

我尝试了以下查询以与表中的NULL条目一起排序。我需要使用book_id对book_name进行排序。

升序：

SELECT book_id 
FROM   books 
GROUP  BY book_id 
ORDER  BY CASE 
            WHEN book_id IS NULL THEN 1 
            ELSE 0 
          END, 
          book_id; 

 1 
 2 
 NULL

预期结果：

升序：

1
2
NULL

降序：

SELECT book_id 
FROM   books 
GROUP  BY book_id 
ORDER  BY CASE 
            WHEN book_id IS NULL THEN 1 
            ELSE 0 
          END DESC, 
          book_id; 




 NULL
 1 
 2

预期结果：

降序：

NULL
2
1

Answer 1

您还可以将DESC排序方向应用于第二个排序列：

SELECT book_id 
FROM   books 
GROUP  BY book_id 
ORDER  BY CASE WHEN book_id IS NULL 
             THEN 1 
             ELSE 0 
          END DESC, 
          book_id DESC; --- !!!

如果省略，则默认为ASC

Answer 2

只需将空值设置为-1，然后根据该值进行排序。例如

 SELECT book_id 
FROM   books 
GROUP  BY book_id 
ORDER  BY isnull(book_id,-1) ASC;

Answer 3

ASC：

SELECT book_id 
FROM   books
order by book_id , COALESCE(book_id,0);

DESC：

SELECT book_id 
FROM   books
order by book_id desc , COALESCE(book_id,0) desc;

Answer 4

您还可以使用以下查询 -

升序

SELECT book_id 
FROM   books 
GROUP  BY book_id 
ORDER  BY IF(book_id IS NULL,1,0), book_id;

降序

SELECT book_id 
FROM   books 
GROUP  BY book_id 
ORDER  BY IF(book_id IS NULL,0,1), book_id DESC;

包含空值的SQL排序

4 个答案: