PDA项目 SQL CE 数据库注意事项

一：注意每次操作SQLCE前都Close一次，因为SQLCE2.0只支持一个连接；

二：检测数据库里是否存在某个表用：select table_name from Information_Schema.Tables；

三：SQLCE2.0 不支持存储过程、触发器等，都要用SQL来实现；

四：从XML转换过来的时间要转换一下：

DateTime dt_c2 = DateTime.Parse(xn.ChildNodes[19].InnerXml);

dt_c2.ToString("G"), //集装箱作业时间

五：SQLCE的字段类型和SQL Server的不一样，具体见SQLCE帮助文档

六：SQLCE不支持Distict 、top 等函数，Distinct可以用GroupBy来实现

七：SQLCE不支持如下语句：

select 'RT' = case when rt1 is not null then rt1 else '' end +
case when rt2 is not null then rt2 else '' end +
case when rt3 is not null then rt3 else '' end +
case when rt4 is not null then rt4 else '' end +
case when rt5 is not null then rt5 else '' end +
case when rt6 is not null then rt6 else '' end +
case when rt7 is not null then rt7 else '' end
from ct_bay

现在是用程序来实现连接的

八：数据库操作部分：

// execute sql, returns first column in first row as an int
private int ExecuteScalarInt(string sql)
{
int result = 0;
object o = this.ExecuteScalar(sql);
if (o != System.DBNull.Value)
result = Convert.ToInt32(o);
return result;
}

// execute sql, returns first column in first row as a string
private string ExecuteScalarString(string sql)
{
string result = String.Empty;
object o = this.ExecuteScalar(sql);
if (o != System.DBNull.Value)
result = Convert.ToString(o);
return result;
}

// execute sql, returns DataSet with result of query
// uses specified tableName for table in DataSet
private DataSet Execute(string tableName, string sql)
{
DataSet ds = new DataSet();
try
{
SqlCeDataAdapter da = GetAdapter(sql);
da.Fill(ds, tableName);
}
catch (SqlCeException ex)
{
HandleError(ex);
}
catch (Exception ex)
{
HandleError(ex);
}
return ds;
}

// execute sql, returns number of rows affected
protected internal int ExecuteNonQuery(string sql)
{
int count=0;
try
{
SqlCeCommand cmd = GetCommand();
cmd.CommandText = sql;
count = cmd.ExecuteNonQuery();
}
catch (SqlCeException ex)
{
HandleError(ex);
}
catch (Exception ex)
{
HandleError(ex);
}
return count;
}

private SqlCeDataReader ExecuteDataReaderSingleRow(string sql)
{
try
{
SqlCeCommand cmd = GetCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = sql;
m_dtr = cmd.ExecuteReader(CommandBehavior.SingleRow);
}
catch (SqlCeException ex)
{
HandleError(ex);
}
catch (Exception ex)
{
HandleError(ex);
}
return m_dtr;
}

// execute sql, returns the first column of the first row
private object ExecuteScalar(string sql)
{
object result=null;
try
{
SqlCeCommand cmd = GetCommand();
cmd.CommandText = sql;
result = cmd.ExecuteScalar();
}
catch (SqlCeException ex)
{
HandleError(ex);
}
catch (Exception ex)
{
HandleError(ex);
}
return result;
}

//
// private helper functions
//

private void OpenConnection()
{
// make sure we have open connection
if (m_con == null)
m_con = new SqlCeConnection(@"Data Source=/Program Files/ChinaTallyPDACSharp/ChinaTallyDB.sdf;");

if (m_con.State == ConnectionState.Closed)
m_con.Open();
}

// return command object
private SqlCeCommand GetCommand()
{
OpenConnection();

// create command object
if (m_cmd == null)
{
m_cmd = new SqlCeCommand();
m_cmd.Connection = m_con;
m_cmd.CommandType = CommandType.Text;
}

m_cmd.CommandText = String.Empty;
return m_cmd;
}

// return data adapter
private SqlCeDataAdapter GetAdapter(string sql)
{
// make sure we have open connection
if (m_con == null)
m_con = new SqlCeConnection(@"Data Source=/Program Files/ChinaTallyPDACSharp/ChinaTallyDB.sdf;");

if (m_con.State == ConnectionState.Closed){
try{
m_con.Open();
}
catch(SqlCeException ex){
throw ex;
}
}
SqlCeDataAdapter scda = new SqlCeDataAdapter(sql, m_con);
return scda;
}