在Asp.net中的SQL查询按钮上单击事件 [英] Sql Query in Asp.net On button Click Event

问题描述

System.Data.SqlClient.SqlException: Operand data type varchar is invalid for sum operator.

代码在这里

And Code is Here

con.Open();
string col = "select SUM(Price) from Purchase where CustomerName = '"+DropDownList1.SelectedItem.Text+"' ";
SqlCommand cmd = new SqlCommand(col,con);
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{

TextBox5.Text = dr[0].ToString();
}
con.Close();
}

推荐答案

您表中的价格"列是文本数据类型(varchar，nvarchar，text)吗?您无法将varchar求和.
SUM只能与数字列一起使用.空值将被忽略.
要在SQL中使用SUM(*)函数，您将必须使用数字数据类型，例如int，decimal，money.

您可以在每次需要对其求和或进行其他数学运算时进行强制转换，但是使用适当的数据类型要好得多.将价格列的数据类型更改为数字数据类型.货币或小数可能是一个不错的选择.

Your column "Price" in your table is a text datatype (varchar, nvarchar, text)? You can''t SUM a varchar.
SUM can be used with numeric columns only. Null values are ignored.
To use the SUM(*) function in SQL you will have to use a numeric datatype like int, decimal, money.

You could cast this every time you need to sum it or do other mathematically operations, but it''s a lot better to use a proper datatype. Change the datatype of your Price column to a numeric datatype. Money or decimal would probably be a good choice.

您的价格列是无法累加的varchar列，请使用以下内容:

Your Price column is a varchar column which cannot be summed, use the following:

string col = "select SUM(CAST( Price AS decimal(3,0)) from Purchase where CustomerName = '"+DropDownList1.SelectedItem.Text+"' ";

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