T-SQL的SQL Server查询错误

Question

当我尝试执行代码时，我收到了一条错误消息......

变量x正常运行并显示预期值，textBoxes也是如此。并且连接是开放的并且正常工作，因为代码块在它工作正常之前！

string x = ViaClass.name;

SqlConnection connection = new SqlConnection();
SqlCommand command = new SqlCommand(); 
connection.ConnectionString = (@"myconString;Integrated Security=YES");
command.Connection = connection;

try
{
    connection.Open();

    command.CommandText = "IF NOT EXISTS (SELECT 1 FROM ADDRESSES WHERE USID =" + "'" + x + "'" +")" + " INSERT INTO ADDRESSES " + "(AddressLine1, AddressLine2, PostCode) VALUES " + " (@AddressLine1, @AddressLine2, @PostCode)";

    command.Parameters.AddWithValue("@AddressLine1", addressLine1TextBox.Text);
    command.Parameters.AddWithValue("@AddressLine2", addressLine2TextBox.Text);
    command.Parameters.AddWithValue("@PostCode", postCodeTextBox.Text);


    int result = command.ExecuteNonQuery();

    if (result > 0) MessageBox.Show("Record successfully added!");
    else MessageBox.Show("Failed to add record!");
}
catch (SqlException ex) 
{
    MessageBox.Show(ex.Message); 
}
finally
{
    connection.Close();
}

我的SQL有什么问题吗？我正在使用SQL Server和C＃

第一个sql的屏幕截图

Answer 1

如果声明：

 IF NOT EXISTS (SELECT 1 FROM ADDRESSES WHERE USID =" + "'" + x + "'" +")

是假的，那么

 result = 0

您的数据是否已存在于数据库中？

---

有关此验证的有效声明，请

 command.CommandText = "IF NOT EXISTS (SELECT 1 FROM ADDRESSES WHERE USID =" + "'" + x + "'" +")" + " INSERT INTO ADDRESSES " + "(AddressLine1, AddressLine2, PostCode) VALUES " + " (@AddressLine1, @AddressLine2, @PostCode) ELSE SELECT 1";

但我不认为有一个＆＃39; IF＆＃39;在更新之前，检查会影响行数，这是检查操作是否成功的好方法。