Powershell和SQL：如何在变量中存储查询的值？

I wrote a powershell script that runs two SQL queries, saves the result in 2 variables and compares them. I receive an email if the results are different from one another.
However, I noticed that the results are always the same. When I Write-Host the two variables, I get this: System.Data.DataRow. I assume that when I compare the two variables, I am actually comparing System.Data.DataRow to System.Data.DataRow.

我编写了一个运行两个SQL查询的powershell脚本，将结果保存在2个变量中并进行比较。如果结果彼此不同，我会收到一封电子邮件。但是，我注意到结果总是一样的。当我写这两个变量时，我得到了这个：System.Data.DataRow。我假设当我比较两个变量时，我实际上是将System.Data.DataRow与System.Data.DataRow进行比较。

The IF I use is quite simple:

我使用的IF非常简单：

if ($resultDB = $resultCube) {$SMTPClient.Send( $emailMessageSuccess )} ELSE {$SMTPClient.Send( $emailMessageFailure )}

Am I doing it wrong, or is there a way to store the actual value of an SQL query in a variable?
When I Write-Output the variables, I get:

我做错了，还是有办法将SQL查询的实际值存储在变量中？当我写输出变量时，我得到：

Column1  
-------  
993991

That number is what I am looking for.

这个号码正是我要找的。

1 个解决方案

#1

This happens, as assignment and comparison operators are mixed. In Powershell, = is assignment and -eq is equal comparison. Thus,

发生这种情况，因为赋值和比较运算符是混合的。在Powershell中，=是赋值，-eq是相等的比较。从而，

if ($resultDB = $resultCube) { ... }

is parsed as

被解析为

if $resultCube was assigned into $resultDB without any issues, do...

If you wonder how assignment could fail, consider read-only variables:

如果您想知道赋值如何失败，请考虑只读变量：

New-Variable -Name myConstant -Value 1
$myConstant
1
if($myConstant = 2) { "aye"} else { "nay" } # Try and assign new value
aye
$myConstant # It works
2
Remove-Variable -Name myconstant
New-Variable -Name myConstant -Value 1 -Option readonly # Now, let's try with a read-only variable
if($myConstant = 2) { "aye"} else { "nay" } # Kaboom!
Cannot overwrite variable myConstant because it is read-only or constant.
At line:1 char:4
+ if($myConstant = 2) { "aye"} else { "nay" }
+    ~~~~~~~~~~~~~~~
    + CategoryInfo          : WriteError: (myConstant:String) [], SessionStateUnauthorizedAccessException
    + FullyQualifiedErrorId : VariableNotWritable

As how to compare column values, try something akin

如何比较列值，尝试类似的东西

if ($resultDB["myColumn"] -eq $resultCube["myColumn"]) { ... }

#1