Question

我有一个像这样的mysql查询 -

SELECT location, 
SUM(IF(action_dt_tm BETWEEN '2013-01-01' AND '2013-06-30',1,0)) AS previous, 
SUM(IF(action_dt_tm BETWEEN '2013-07-01' AND '2013-12-31',1,0)) AS current, 
SUM(IF(action_dt_tm BETWEEN '2013-07-01' AND '2013-12-31',1,0))- 
SUM(IF(action_dt_tm BETWEEN '2013-01-01' AND '2013-06-30',1,0)) as diff, ( 
SUM(IF(action_dt_tm BETWEEN '2013-07-01' AND '2013-12-31',1,0))- 
SUM(IF(action_dt_tm BETWEEN '2013-01-01' AND '2013-06-30',1,0)))/ 
SUM(IF(action_dt_tm BETWEEN '2013-01-01' AND '2013-06-30',1,0))*100 AS percent 
FROM table group by location order by percent DESC

我基于stackoverflow上的先前答案。

这个想法是返回一个位置，一个前一个日期范围计数，一个当前计数（这些范围改变），先前和当前之间的数字差异以及％增加或减少。

像 -

LOCATION 1     38    27    -11    -28.94%
LOCATION 2     6     18     12    200.00%

等

上面的代码，虽然可能很笨，但似乎有效，除了发现PREVIOUS计数为零，然后百分比返回为NULL，而不是增加/减少。

即

LOCATION 3     0     32      32     (NULL)

任何人都可以建议如何更改查询以解决此问题。

Answer 1

如果您之前的值等于0，则会导致百分比列除以零。

默认情况下，除以零会产生NULL结果并且没有警告。

https://dev.mysql.com/doc/refman/5.0/en/precision-math-expressions.html

由于你有一个除零，我不确定是否有意义替换任何其他的NULL值，但你应该能够通过在进行除法之前检查前一个计数的零来替换它。

示例（将其替换为零）：

SELECT location, 
SUM(IF(action_dt_tm BETWEEN '2013-01-01' AND '2013-06-30',1,0)) AS previous, 
SUM(IF(action_dt_tm BETWEEN '2013-07-01' AND '2013-12-31',1,0)) AS current, 
SUM(IF(action_dt_tm BETWEEN '2013-07-01' AND '2013-12-31',1,0))- 
SUM(IF(action_dt_tm BETWEEN '2013-01-01' AND '2013-06-30',1,0)) as diff, ( 
case 
  when (SUM(IF(action_dt_tm BETWEEN '2013-01-01' AND '2013-06-30',1,0))) then
    0
  else
    SUM(IF(action_dt_tm BETWEEN '2013-07-01' AND '2013-12-31',1,0))- 
    SUM(IF(action_dt_tm BETWEEN '2013-01-01' AND '2013-06-30',1,0)))/ 
    SUM(IF(action_dt_tm BETWEEN '2013-01-01' AND '2013-06-30',1,0))*100
end
 AS percent 
FROM table group by location order by percent DESC

第一个SUM为零的2个日期之间的SUM增加/减少百分比

1 个答案: