从sqlite读取数据到C＃然后到sqlite

Question

Reproducible Example:

sqlite db test3.s3db has one table with name "MathRec":

name score
Bill 2
Mary 3
John 3

Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.SQLite;

namespace ConsoleApplication7

{
    class Program
    {
    static void Main(string[] args)
    {

        string fullPath = "C:\\Users\\Desktop\\dataset\\test3.s3db";
        SQLiteConnection conread = new SQLiteConnection("Data Source=" + fullPath);
        conread.Open();

        string selectSQL = "SELECT * FROM MathRec";
        SQLiteCommand selectCommand = new SQLiteCommand(selectSQL, conread);
        SQLiteDataReader dataReader = selectCommand.ExecuteReader();
        DataSet ds = new DataSet();
        DataTable dt = new DataTable("MathRec");
        dt.Load(dataReader);
        ds.Tables.Add(dt);



        // Create a table in the database to receive the information from the DataSet

        string fullPath2 = "C:\\Users\\\\Desktop\\dataset\\test4.s3db";
        SQLiteConnection conwrite = new SQLiteConnection("Data Source=" + fullPath2);
        conwrite.Open();
        SQLiteCommand cmd = new SQLiteCommand(conwrite);
        cmd.CommandText = "DROP TABLE IF EXISTS MathRec";
        cmd.ExecuteNonQuery();
        cmd.CommandText = "CREATE TABLE MathRec(name text , score integer)";
        cmd.ExecuteNonQuery();
        SQLiteDataAdapter adaptor = new SQLiteDataAdapter("SELECT * from MathRec", conwrite);
        adaptor.InsertCommand = new SQLiteCommand("INSERT INTO MathRec  VALUES(:name, :score)", conwrite);
        adaptor.InsertCommand.Parameters.Add("name", DbType.String, 0, "name");
        adaptor.InsertCommand.Parameters.Add("score", DbType.Int32, 0, "score");
        adaptor.Update(ds, "MathRec");



         }

    }
 }

Questions: Table MathRec is created in test4.s3db with column names: name and socre, but the table is empty with no records inserted.

Help is needed!

Please don't ask me why I am just copying one db to another, because I am testing one part of the code for a bigger project, where I will do calculations to the Dataset in the middle step in the future.

Thanks!

---

To simplify the question:

This works (use datatable and adapter to update the original sqlite table):

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SQLite;
using System.Data;

namespace ConsoleApplication7
{
    class Program
    {
        static void Main(string[] args)
        {
            string fullPath = "C:\\Users\\data\\test.db";
            SQLiteConnection conread = new SQLiteConnection("Data Source=" + fullPath);
            conread.Open();


        SQLiteDataAdapter DB = new SQLiteDataAdapter("SELECT speed, dist FROM Cars2", conread);
        DataSet DS = new DataSet();

        DB.Fill(DS, "NewCars");


        object[] rowVals = new object[2];
        rowVals[0] = 10;
        rowVals[1] = 20;
        DS.Tables["NewCars"].Rows.Add(rowVals);


        DB.InsertCommand = new SQLiteCommand("INSERT INTO Cars2 (speed, dist)  
                                 " + " VALUES (:speed,  :dist)", conread);
        DB.InsertCommand.Parameters.Add("speed", DbType.Double, 0, "speed");
        DB.InsertCommand.Parameters.Add("dist", DbType.Double, 20, "dist");
        DB.Update(DS, "NewCars");



        }
    }
}

And this works (create a new sqlite table from old one):

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SQLite;
using System.Data;

namespace ConsoleApplication7
{
    class Program
    {
        static void Main(string[] args)
        {
            string fullPath = "C:\\Users\\data\\test.db";
            SQLiteConnection conread = new SQLiteConnection("Data Source=" + fullPath);
            conread.Open();


        SQLiteCommand cmd = new SQLiteCommand(conread);
        cmd.CommandText = "DROP TABLE IF EXISTS Cars";
        cmd.ExecuteNonQuery();
        cmd.CommandText = "CREATE TABLE Cars (speed REAL , dist REAL)";
        cmd.ExecuteNonQuery();
        cmd.CommandText = "INSERT INTO Cars SELECT * from DS";
        cmd.ExecuteNonQuery();
        cmd.Dispose();
        }
    }
}

But this one is what I wanted (use datatable and adapter to create new table in sqlite) and is not working:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SQLite;
using System.Data;

namespace ConsoleApplication7
{
    class Program
    {
        static void Main(string[] args)
        {
            string fullPath = "C:\\Users\\data\\test.db";
            SQLiteConnection conread = new SQLiteConnection("Data Source=" + fullPath);
            conread.Open();
    SQLiteDataAdapter DB = new SQLiteDataAdapter("SELECT speed, dist FROM Cars2", conread);
    DataSet DS = new DataSet();

    DB.Fill(DS, "NewCars");


    object[] rowVals = new object[2];
    rowVals[0] = 10;
    rowVals[1] = 20;
    DS.Tables["NewCars"].Rows.Add(rowVals);


   SQLiteDataAdapter DB2 = new SQLiteDataAdapter("SELECT speed, dist FROM Cars3", conread);
    DB2.InsertCommand = new SQLiteCommand("INSERT INTO Cars3 (speed, dist)  
                        " + " VALUES (:speed,  :dist)", conread);
    DB2.InsertCommand.Parameters.Add("speed", DbType.Double, 0, "speed");
    DB2.InsertCommand.Parameters.Add("dist", DbType.Double, 20, "dist");
    DB2.Update(DS, "NewCars");


    }
}
}

Please help!!!

Answer 1

I found the answer!

Adapter.Update can only be used to update the original table in the database and not to save the datatable in a new one. Please refer to the thread for answers:

C# Dataset to Access DB

Cheers!

Answer 2

The easiest way to copy one table to another database is to attach the second database to the first connection, and copy the data directly:

ATTACH '...\test4.s3db' AS 'test4';
DROP TABLE IF EXISTS test4.MathRec;
CREATE TABLE test4.MathRec(name text , score integer);
INSERT INTO test4.MathRec SELECT * FROM MathRec;

If you want to do calculations, you might be able to do them in SQL, in the SELECT statement. If not, you have to read the data with a SELECT and then execute one INSERT statement for each record to be written. (In that case, you don't need the ATTACH .)