SQL高手请进：sql能在access里执行，在代码曝“无效的null使用”，即查不出结果出来

ReynoldCQ 2015-04-22 11:22:26

SQL语句：

string queryStringRgt = @"SELECT TB_YWDA.ywda_SeqNO as 顺序号, TB_YWDAJ.ywdaj_DirName as 档号, TB_YWDAJ.ywdaj_KeepPeriod as 保管期限, TB_YWDAJ.ywdaj_Year as 年度, "

                    + " TB_YWDA.ywda_Responsible as 责任者, TB_YWDA.ywda_Title as 题名, TB_YWDA.ywda_PageNO as 页号, TB_YWDAJ.ywdaj_Type as 档案类别, "

                    + " TB_YWDA.ywda_PageSum as 页数,  TB_YWDA.ywda_CreatedTime as 成文时间, TB_YWDA.ywda_ID, TB_YWDA.ywdaj_ID FROM TB_YWDA left join TB_YWDAJ on TB_YWDA.ywdaj_ID = TB_YWDAJ.ywdaj_ID  where CInt(TB_YWDA.ywdaj_ID) = '" + selectedYwdajID + "'";

数据加载代码：

OleDbCommand SQLQuery = new OleDbCommand();

            DataTable data = new DataTable();

            

            this.skinDataGridViewRgt.DataSource = null;

            SQLQuery.Connection = null;

            OleDbDataAdapter dataAdapter = null;

            this.skinDataGridViewRgt.Columns.Clear(); // <-- clear columns

            //---------------------------------       

            SQLQuery.CommandText = sqlQueryString;

            SQLQuery.Connection = dataBase;

            dataAdapter = new OleDbDataAdapter(SQLQuery);

            MessageBox.Show("hah");

            dataAdapter.Fill(data);          //问题出在这一行

            skinDataGridViewRgt.DataSource = data;

之前另一个sql语句时，都没有错误，改了之后就出现问题了，谢谢大神帮忙解决一下。

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ReynoldCQ 2015-05-04

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谢谢@Tiger_Zhao @ky_min 确实是因为有TB_YWDA.ywdaj_ID为空了所导致

Tiger_Zhao 2015-04-24

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CInt(TB_YWDA.ywdaj_ID) 为什么要加 CInt？这个字段不应该本来就设计为Int类型吗？
如果TB_YWDA.ywdaj_ID有空值，加了 CInt() 就会报“无效的null使用”！

还在加载中灬 2015-04-24

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不知道是不是不能正常处理NULL，看下ACCESS以下查询有没有结果

SELECT
	TB_YWDA.ywda_SeqNO as 顺序号
	, TB_YWDAJ.ywdaj_DirName as 档号
	, TB_YWDAJ.ywdaj_KeepPeriod as 保管期限
	, TB_YWDAJ.ywdaj_Year as 年度
	, TB_YWDA.ywda_Responsible as 责任者
	, TB_YWDA.ywda_Title as 题名
	, TB_YWDA.ywda_PageNO as 页号
	, TB_YWDAJ.ywdaj_Type as 档案类别
	, TB_YWDA.ywda_PageSum as 页数
	, TB_YWDA.ywda_CreatedTime as 成文时间
	, TB_YWDA.ywda_ID
	, TB_YWDA.ywdaj_ID
FROM TB_YWDA
	left join TB_YWDAJ on TB_YWDA.ywdaj_ID = TB_YWDAJ.ywdaj_ID
where CInt(TB_YWDA.ywdaj_ID) = 'selectedYwdajID'
	AND TB_YWDAJ.ywdaj_ID IS NULL

ReynoldCQ 2015-04-24