除以零时遇到错误，但应按 CASE 排除

Question

我有以下代码，但出现错误：

Divide by zero error encountered.

SELECT
CASE WHEN SUM([monthly_qty]) = 0 THEN 999 
ELSE ROUND(SUM([monthly_buy] * ([monthly_markup]+100)/100),2) * SUM([monthly_qty] / [monthly_qty]) END as [monthly_total]
FROM [xxxxx].[dbo].[quote_items] WHERE docid='10152'

导致错误的字段是第二个 [monthly_qty]，就在 CASE 语句的 END 之前。

SUM([monthly_qty] / **[monthly_qty]**)

monthly_qty 的值为零，所以错误是有道理的，但我很困惑，因为这个字段在 CASE 语句中，所以预期结果是 999

非常感谢任何帮助。

Answer 1

阅读 MS Docs，备注下有您的案例示例。

The CASE expression evaluates its conditions sequentially and stops with the first condition whose condition is satisfied. In some situations, an expression is evaluated before a CASE expression receives the results of the expression as its input. Errors in evaluating these expressions are possible. Aggregate expressions that appear in WHEN arguments to a CASE expression are evaluated first, then provided to the CASE expression. For example, the following query produces a divide by zero error when producing the value of the MAX aggregate. This occurs prior to evaluating the CASE expression.

Answer 2

我无法理解您代码中某些部分的原因，例如：

SUM([monthly_qty] / [monthly_qty])

当[monthly_qty] = 零时结果错误，非零时为1。

无论如何，当“monthly_qty”为零时，您可以设置一个默认值：

IIF([monthly_qty]= 0,'YOUR_DEFAULT_VALUE', [monthly_qty] / [monthly_qty])

然后：

SUM(IIF([monthly_qty]= 0,'YOUR_DEFAULT_VALUE', [monthly_qty] / [monthly_qty]))

Answer 3

原因很简单。此代码：

SUM([monthly_qty]) = 0

不阻止此代码中的除数为零：

SUM([monthly_qty] / [monthly_qty])

表达方式不同

最简单的解决方案（本质上是“标准”方法）是使用 NULLIF():

SUM([monthly_qty] / NULLIF([monthly_qty], 0))

不过，不知道你是不是真的打算：

SUM([monthly_qty]) / NULLIF(SUM([monthly_qty]), 0)

除以零时遇到错误，但应按 CASE 排除

Divide by zero error encountered, but should be excluded by CASE

sql

sql-server

tsql

case

divide