Question

过滤两个日期之间的数据，出现以下错误：

System.Data.SqlClient.SqlException：varchar数据的转换类型转换为日期时间数据类型会导致超出范围。

我的代码是：

con.Open();
SqlCommand cmd = con.CreateCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = "SELECT daytime AS DATE, COLUMN_2 AS SHIFT, COLUMN_3 AS 'PART NO',COLUMN_4 AS 'PART NAME',BSNO AS 'BASKET NUMBER',Spare1 AS MATERIAL, CAS6 AS 'CASCADE RINSE 6 TIME (sec)',DRY AS 'DRYER TIME (sec)',TEMP1 AS 'DRYER TEMP (°c)' FROM Table_2 WHERE daytime BETWEEN '" + dateTimePicker1.Value.ToString() + "' AND '" + dateTimePicker2.Value.ToString() + "'";
cmd.ExecuteNonQuery();
DataTable dt = new DataTable();
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);
metroGrid1.DataSource = dt;
con.Close();

我无法解决此错误。

Answer 1

每当发现将.Net DateTime值转换为用于SQL的字符串时，您所做的事情非常错误。

下面演示的模式对问题代码进行了一些改进。最值得注意的是，问题中的代码容易受到sql注入攻击的攻击，而此代码则并非如此。但是这里也有其他改进。

//most datetime comparisons want an *exclusive* upper bound, but the BETWEEN operator bounds are inclusive on both ends
var sql = "SELECT daytime AS DATE, COLUMN_2 AS SHIFT, COLUMN_3 AS 'PART NO',COLUMN_4 AS 'PART NAME',BSNO AS 'BASKET NUMBER',Spare1 AS MATERIAL, CAS6 AS 'CASCADE RINSE 6 TIME (sec)',DRY AS 'DRYER TIME (sec)',TEMP1 AS 'DRYER TEMP (°c)' FROM Table_2 WHERE daytime >= @daytimeStart AND daytime < @daytimeEnd ;";
var dt = new DataTable();

//Don't try to re-use your connection object. 
// ADO.Net connection pooling means you should create a new connection for most queries
using (var con = new SqlConnection("connection string here"))
using (var cmd = new SqlCommand(sql, con))
using (var da = new SqlDataAdapter(cmd))
{  //These using blocks guarantee the connection is closed, **even if an exception is thrown**. The original code would have left the connection open if you had an exception.

    //This is the correct way to include user data with your sql statement
    // **NEVER** use string concatenation to substitute values into SQL strings
    cmd.Parameters.Add("@daytimeStart", SqlDbType.DateTime).Value =  dateTimePicker1.Value;
    cmd.Parameters.Add("@daytimeEnd", SqlDbType.DateTime).Value =  dateTimePicker2.Value;

    //the Fill() method opens and closes the connection as needed
    da.Fill(dt);
}
metroGrid1.DataSource = dt;

这里还是没有多余的注释，因此您可以看到新模式与问题中的原始代码相比不会显着更长：

var sql = "SELECT daytime AS DATE, COLUMN_2 AS SHIFT, COLUMN_3 AS 'PART NO',COLUMN_4 AS 'PART NAME',BSNO AS 'BASKET NUMBER',Spare1 AS MATERIAL, CAS6 AS 'CASCADE RINSE 6 TIME (sec)',DRY AS 'DRYER TIME (sec)',TEMP1 AS 'DRYER TEMP (°c)' FROM Table_2 WHERE daytime >= @daytimeStart AND daytime < @daytimeEnd ;";

var dt = new DataTable();
using (var con = new SqlConnection("connection string here"))
using (var cmd = new SqlCommand(sql, con))
using (var da = new SqlDataAdapter(cmd))
{   
    cmd.Parameters.Add("@daytimeStart", SqlDbType.DateTime).Value =  dateTimePicker1.Value;
    cmd.Parameters.Add("@daytimeEnd", SqlDbType.DateTime).Value =  dateTimePicker2.Value;

    da.Fill(dt);
}
metroGrid1.DataSource = dt;

System.Data.SqlClient.SQLException：将varchar数据类型转换为datatime

1 个答案: