Question

我需要替换所有等于NULL值“ 0”的可能结果。最好的选择是什么？在这种情况下，请使用case语句或replace命令：

SELECT name, COUNT(IF(stat='open',1, NULL)) 'open',
       COUNT(IF(stat='close',1, NULL)) 'close',
       COUNT(IF(stat='all',1, NULL)) 'all',
       COUNT(IF(stat='reopen',1, NULL)) 'reopen',
       COUNT(IF(stat='finish',1, NULL)) 'finish'
FROM dashboard group by name order by name = 'Party' desc

+----------+------+-------+-----+--------+--------+
| name     | open | close | all | reopen | finish |
+----------+------+-------+-----+--------+--------+
| Party    |   21 |     0 |   0 |      0 |      0 |
+----------+------+-------+-----+--------+--------+

Answer 1

您可以使用NULLIF()功能。

SELECT name, 
       NULLIF(COUNT(IF(stat='open',1, NULL)), 0) 'open',
       NULLIF(COUNT(IF(stat='close',1, NULL)), 0) 'close',
       NULLIF(COUNT(IF(stat='all',1, NULL)), 0) 'all',
       NULLIF(COUNT(IF(stat='reopen',1, NULL)), 0) 'reopen',
       NULLIF(COUNT(IF(stat='finish',1, NULL)), 0) 'finish'
FROM dashboard 
group by name 
order by name = 'Party' desc

NULLIF()返回第一个值，除非它等于第二个值，然后返回NULL。

顺便说一句，您可以将COUNT(IF(stat='xxx', 1, NULL))简化为SUM(stat='xxx')。

Answer 2

一种方法使用NULLIF()：

SELECT name,
       NULLIF(SUM(stat = 'open'), 0) as open,
       NULLIF(SUM(stat = 'close'), 0) as close,
       NULLIF(SUM(stat = 'all'), 0) as all,
       NULLIF(SUM(stat = 'reopen'), 0) as reopen,
       NULLIF(SUM(stat = 'finish'), 0) as finish
FROM dashboard 
GROUP BY name 
ORDER BY name = 'Party' desc;

另一个人使用CASE：

SELECT SUM(CASE WHEN stat = 'open' THEN 1 END) as open,
       . . .

查询后替换内容

2 个答案: