c# - MySQL 跳过空字符串查询？

Question

所以我设置了一个应用程序来导入 CSV 文件。它创建一个数据表和一个临时 SQL 表。该代码读取 CSV 并将其放入数据表中，然后将其批量导入到临时表中，到目前为止，临时表只是将其复制到生产表中。出于我的目的，我需要它，以便当导入 .csv 文件并且存在空字符串时，它们会被跳过，不会在生产数据库中插入或更新，并且仅插入/更新 csv 中存在的内容(禁止类(class))。

例如，假设我第一次导入时，我只是简单地导入了以下站点信息:

PDW0033B50D3,Northeast office,246 Western Blvd

然后稍后我想更新该位置的地址，因此我重新导入了仅包含必要字段的 csv 文件。

PDW0033B50D3,,290 Western Blvd

现在，当第二行为空时，代码将在数据库中放入一个空字符串，因此 Northeast office 将在数据库中变成空白/空字符串。如何做到这一点，以便当 csv 中存在空字符串时，它会通过我的 sql 查询跳过？

这是我的代码:

       public void btnBulkSite_click(object sender, EventArgs e)
    {
            //Save File
        if (FileUpLoad1.HasFile)
        {
            FileUpLoad1.SaveAs(@"C:\temp\" + FileUpLoad1.FileName);
            btnBulkSite.Text = "File Uploaded: " + FileUpLoad1.FileName;
        }
        else
        {
            btnBulkSite.Text = "No File Uploaded.";
        }

            //Create Temporary Table

        string TmpTable = "CREATE TABLE #TMPBULK (SERVER_ID VARCHAR(13), SITE_NAME VARCHAR(50), SITE_ADDRESS VARCHAR(50))";
            //Create DataTable
        DataTable tblcsv = new DataTable();

        tblcsv.Columns.Add(new DataColumn("SERVER_ID", typeof(string)));
        tblcsv.Columns.Add(new DataColumn("SITE_NAME", typeof(string)));
        tblcsv.Columns.Add(new DataColumn("SITE_ADDRESS", typeof(string)));



            //Read in CSV File
        System.IO.StreamReader stream = new System.IO.StreamReader(FileUpLoad1.PostedFile.InputStream);

        string ReadCSV = stream.ReadToEnd();
        foreach (string csvRow in ReadCSV.Split('\n'))
            {

                if (!string.IsNullOrEmpty(csvRow))
                {
                tblcsv.Rows.Add();
                int count = 0;

                foreach (string FileRec in csvRow.Split(','))
                {
                    tblcsv.Rows[tblcsv.Rows.Count - 1][count] = FileRec;

                    count++;
                }
            }
        }

            //SQL CON
        string conString = ConfigurationManager.ConnectionStrings["css"].ConnectionString;
        using (SqlConnection con2 = new SqlConnection(conString))
        {
            con2.Open();

            //Execute the command to make a temp table
            SqlCommand cmd = new SqlCommand(TmpTable, con2);
            cmd.ExecuteNonQuery();
            using (BulkOperation bulk = new BulkOperation(con2))

            {


                bulk.DestinationTableName = "#TMPBULK";

                bulk.BulkInsert(tblcsv);
            }

            //Copy Data from Temp Table to Prod Table
            string mergeSql = "merge into SITE_INFO as Target " +
              "using #TMPBULK as Source " +
              "on " +
              "Target.SERVER_ID=Source.SERVER_ID " +
              "and Target.SITE_NAME = Source.SITE_NAME " +
              "when matched then " +
              "update set Target.SITE_ADDRESS=Source.SITE_ADDRESS " +
              "when not matched then " +
              "insert (SERVER_ID,SITE_NAME,SITE_ADDRESS) values (Source.SERVER_ID,Source.SITE_NAME,Source.SITE_ADDRESS);";






            cmd.CommandText = mergeSql;
            cmd.ExecuteNonQuery();
            cmd.CommandText = "drop table #TMPBULK";
            cmd.ExecuteNonQuery();
        }
    }

Answer 1

尝试更改您的设置

update set Target.SITE_ADDRESS=Source.SITE_ADDRESS

至

update set Target.SITE_ADDRESS=IF(Source.SITE_ADDRESS='',Target.SITE_ADDRESS,Source.SITE_ADDRESS)

对于 SITE_NAME 也是如此。