使用表中的where子句计算行

Question

我试图计算SomeColumn=SomeValue的行数。我的代码如下所示。它没有显示任何内容。

using (SqlConnection conn = new SqlConnection("ConnectionString"))
{
    conn.Open();
    string selectStatement = "Select count(*) from Jobs where 'JobCategory=cse'";

    SqlCommand cmd = new SqlCommand(selectStatement, conn);
    int count = (int)cmd.ExecuteScalar();
    Label1.Text = count.ToString();

    conn.Close();

我应该采取什么步骤？

Answer 1

将'JobCategory = cse'更改为JobCategory ='cse'

喜欢

string selectStatement = "Select count(*) from Jobs where JobCategory = 'cse'";

或尝试这样

string selectStatement = "Select count(*) from Jobs where JobCategory Like 'cse'";

在SQL中检查一次查询，然后在代码中实现它。是否获得预期结果。

Answer 2

您的单引号位置错误。试试这个;

string selectStatement = "Select count(*) from Jobs where JobCategory = 'cse'";

请始终参数化您的SQL查询。这可能是SQL Injection攻击的原因。在这里你可以如何使用它;

string realcse = "Write here which value you want to filter in where clause";
string selectStatement = "Select count(*) from Jobs where JobCategory = @cse";
SqlCommand cmd = new SqlCommand(selectStatement, conn);
cmd.Parameters.AddWithValue("@cse", realcse);

在你的情况下，它应该是;

string realcse = "cse";
cmd.Parameters.AddWithValue("@cse", realcse);

Answer 3

string selectStatement = "Select COUNT(*) from [Jobs] where JobCategory='cse'";

Answer 4

请使用此

string selectStatement = "Select  COUNT(*) as cnt from [Jobs] where JobCategory='cse'";