SQL MAX函数 [英] SQL MAX Function

问题描述

你好，



我试图从我的Customer表中的custID列中获取最高值，然后将其保存为整数。

  Dim  getHighAccountNo  As  SqlCommand = AccountsTableAdapter.Connection.CreateCommand（）
 
 getHighAccountNo.CommandType = CommandType.Text 
 
 custID = getHighAccountNo.CommandText =    SELECT MAX（custID）AS HighestAccountID FROM Customer 
 
 '  custID = getHighAccountNo.CommandText =SELECT IDENT_CURRENT（'Customer'）as LastIdentity 
 
 lblHighestAccountNo.Text = custID.ToString（） 

由于上面的代码总是返回0，我不确定我做错了什么。



感谢任何帮助，



感谢Glen。

解决方案

您定义命令文本，但我看不到您实际执行命令的位置并获取其结果。< br $> b $ b

可能：

 getHighAccountNo.CommandText =   SELECT MAX（custID）AS HighestAccountID FROM Customer 
  int  cutomerId = getHighAccountNo.ExecuteScalar （）; 
 lblHighestAccountNo.Text = customerId.ToString（）; 

希望这有帮助。

< blockquote>您缺少ExecuteScalar。下面的代码应该这样做！

  Dim  getHighAccountNo  As  SqlCommand = AccountsTableAdapter.Connection.CreateCommand（）
 
 getHighAccountNo.CommandType = CommandType.Text 
 
 getHighAccountNo.CommandText =   SELECT MAX（custID）AS HighestAccountID FROM Customer 
  custID = getHighAccountNo.ExecuteScalar（）  
 
 '  custID = getHighAccountNo.CommandText =SELECT IDENT_CURRENT（'Customer' ）作为LastIdentity 
 
 
 lblHighestAccountNo.Text = custID.ToString（）

谢谢你们！那很有效！我很傻！本来应该注意到的！



再次感谢！

Hello,

I am trying to get the highest value from my custID column in my Customer table and to then save this out to an integer.

Dim getHighAccountNo As SqlCommand = AccountsTableAdapter.Connection.CreateCommand()

        getHighAccountNo.CommandType = CommandType.Text

        custID = getHighAccountNo.CommandText = "SELECT MAX(custID) AS HighestAccountID FROM Customer"

        'custID = getHighAccountNo.CommandText = "SELECT IDENT_CURRENT('Customer') as LastIdentity"

        lblHighestAccountNo.Text = custID.ToString()

I'm not sure what I have done wrong as the code above always returns 0.

Any help is appreciated,

Thanks Glen.

解决方案

You define the command text, but I cannot see where you actually execute the command and fetch its result.

Maybe:

getHighAccountNo.CommandText = "SELECT MAX(custID) AS HighestAccountID FROM Customer"
int cutomerId = getHighAccountNo.ExecuteScalar();
lblHighestAccountNo.Text = customerId.ToString();

Hope this helps.

You are missing "ExecuteScalar". The code below should do!

Dim getHighAccountNo As SqlCommand = AccountsTableAdapter.Connection.CreateCommand()

        getHighAccountNo.CommandType = CommandType.Text

        getHighAccountNo.CommandText = "SELECT MAX(custID) AS HighestAccountID FROM Customer"
        custID = getHighAccountNo.ExecuteScalar()

        'custID = getHighAccountNo.CommandText = "SELECT IDENT_CURRENT('Customer') as LastIdentity"

         
        lblHighestAccountNo.Text = custID.ToString()

Thanks guys! That worked! I am silly! Should have noticed that one!

Thanks again!

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