Question

我正在查询数据，如果数据不存在，我插入它。如果是的话，我会做点别的事情：

SqlCommand checkHead = new SqlCommand("SELECT * FROM TABLE WHERE ORDER_NO = '" + orderNo + "';", connection);
SqlDataReader checkHeadReader = checkHead.ExecuteReader(CommandBehavior.SingleRow);

if (!checkHeadReader.HasRows)
{
    checkHeadReader.Close();
    addHead.ExecuteNonQuery();
}

但是我想知道是否有更短的编码方式？下面的代码会起作用吗？

SqlCommand checkHead = new SqlCommand("SELECT * FROM TABLE WHERE ORDER_NO = ' + orderNo + "';", connection);

if(checkHead.ExecuteReader(CommandBehavior.SingleRow).HasRows)
    addHead.ExecuteNonQuery();
else //this order already exists
    Server.Transfer(@"~/Views/Error.aspx");

Answer 1

ExecuteScalar非常适用于此，例如

using (SqlCommand cmdCheck = new SqlCommand("Select Count(*) From Table Where Order_No = '" + orderNo + "'", connection))
{
    int nExists = (int)cmdCheck.ExecuteScalar();
    if (nExists==0) addHead.ExecuteNonQuery();
}

缩短数据访问代码......这会有用吗？

1 个答案: