I created an scheduler application with SQL server and now i want to make another one using SQLite. I have a convert query in SQL and it does not work in SQLite. Can anyone help?
try
{
ObservableCollection<Classes.EventClass> listEvents = new ObservableCollection<EventClass>();
SQLiteConnection conn = new SQLiteConnection(#"Data Source=Scheduler.db;Version=3;");
string query= "Select * from Sche_Event where CONVERT(DATE,Event_TimeFrom) = CONVERT(DATE,'" +d.ToString("yyyy-MM-dd HH:mm:ss") + "') ORDER BY Event_TimeFrom ASC";
SQLiteCommand command= new SQLiteCommand(query, conn);
conn.Open();
SQLiteDataReader dr = command.ExecuteReader();
while (dr.Read())
{
EventClass dog = new EventClass();
dog.DogID = dr.GetInt32(0);
dog.DogName = dr.GetString(1);
dog.DogText = dr.GetString(2);
dog.DogPriority = dr.GetInt32(3);
dog.DogTimeFrom = dr.GetDateTime(4);
dog.DogTimeTo = dr.GetDateTime(5);
dog.KliID = dr.GetInt32(6);
listEvents .Add(dog);
}
return listEvents ;
}
catch (Exception)
{
return null;
}
I expect that my code goes to While() and read the information about the Event but all it does it goes to Catch() and returns nothing.
The query in SQL works just fine but i dont not work with SQLite :(
Of course the statement doesn't work in SQLite, because convert() is not a known function there. But if you're lucky you don't even need it, depending on the format in which the timestamp is stored in your SQLite table. As you didn't provide any sample data nor described what you actually want to do, you could either read the SQLite doc about date and time functions or rephrase your question to "How do I do X in SQLite?".
Related
I have a table containing name, surname and email. I want to retrieve them from the table and so i write:
if (LoginAs.SelectedValue == "Administrator")
{
string result;
string query = "Select * from AdminTable where ID='"+ idBox.Text +"'";
cmd1 = new SqlCommand(query, con);
result = Convert.ToString(cmd1.ExecuteScalar());
Response.Redirect("Admin.aspx");
//Admin user = new Admin(idBox.Text, "Active", mail, firstName, LastName, passwordBox.Text);
}
The problem is, it only returns the name field of the specified row even though i wrote "Select *". What is wrong here?
ExecuteScalar returns just the first column of the first row, and ignores the rest.
So you should use ExecuteReader method. An example from MSDN:
using (SqlConnection connection = new SqlConnection(
connectionString))
{
connection.Open();
SqlCommand command = new SqlCommand(queryString, connection);
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
Console.WriteLine(String.Format("{0}", reader[0]));
}
}
Note that the while (reader.Read()) checks whether your query returned (more) results and positions the cursor on the next record, that you can then read. This example prints the first column's value.
The using statement makes sure the connection is closed after use, whatever happens.
Also, don't build your query directly with input from the user (such as the value of a TextBox), use parameters instead to prevent SQL injection attacks.
You must try ExecuteReader() instead of using ExecuteScalar()
ExecuteScaler is used in situation where we have to read a single value.eg:
select count(*) from tablename.
while
ExecuteReader is used for any result set with multiple rows/columns
(e.g., SELECT * from TableName)
Sample code:
string myQuery="Select * from AdminTable where ID=#myid";
SqlCommand cmd=new SqlCommand(myQuery,conn);
cmd.Parameters.AddWithValue("#myid", value);
conn.Open();
SqlDataReader dreader;
dreader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
while (dreader.Read())
{
string Value1= dreader["COl1"].ToString();
string Value2= dreader["COl2"].ToString();
}
dreader.Close();
Always use parameterized Query
You may try cmd1.ExecuteReader() instead.
I use Sqlite v1.0.79 and vs2010 to create a simple winform application.
I have a customer table, and want to use the SQLiteDataAdapter to easily insert, update and delete records. So i do not need to type the whole insert, update and delete statements.
So i have a Customer class with a static load function that returns a dataset.
private static SQLiteDataAdapter _Adapter;
internal static DataSet Load(long id)
{
var q = "SELECT * FROM Customer WHERE id = {0}".FormatInvariant(id);
var cmd = new SQLiteCommand();
cmd.Connection = [_Connection];
cmd.CommandType = CommandType.Text;
cmd.CommandTimeout = 10;
cmd.CommandText = commandText;
return cmd; _Adapter = new SQLiteDataAdapter();
_Adapter.SelectCommand = cmd;
var ds = new DataSet();
_Adapter.Fill(ds, "Customer");
if (id == 0)
{
ds.AddRow(ds.NewRow());
}
var b = new SQLiteCommandBuilder(_Adapter);
_Adapter.AcceptChangesDuringUpdate = true;
_Adapter.InsertCommand = b.GetInsertCommand();
_Adapter.UpdateCommand = b.GetUpdateCommand();
_Adapter.DeleteCommand = b.GetDeleteCommand();
// Commented out code for note A:
////ds.SetRowValue("lastname", "blaat44");
////_Adapter.Update(ds, "Customer");
return ds;
}
After calling the Load method, the DataSet is used in bindings on a windows form. And after some changes, the Save method is called, where the changes supposed to be saved.
internal static void Save(DataSet data)
{
//// data.AcceptChanges();
_Adapter.Update(data, "Customer");
}
But after the update, the database is not updating anything. What am i missing? I already tried the data.AcceptChanges before the update, but nothing works.
btw. the dataset in the save methods does have the 'right' values, but the update or insert is not working....
The strange thing is if i change a field in the dataset in the Load method (the commented out code at Note A in the example above), the data is saved correctly.
Im not an expert and have a basic understanding of sqlite etc but could the problem be that you are passing the dataset to the save function so the adapter is using a copy maybe of the original dataset. Which is why it works in the load method as the adapter is acessing tje original dataset?
Again this maybe complete babble and i may not understand but ive found sometimes the uneducated answer is a very good push in the right direction
I have a *.MDB database file, and I am wondering if it is possible or recommended to work against it using LINQ in C#. I am also wondering what some simple examples would look like.
I don't know a lot about LINQ, but my requirements for this task are pretty simple (I believe). The user will be passing me a file path to Microsoft Access MDB database and I would like to use LINQ to add rows to one of the tables within the database.
What you want is a LINQ to ODBC provider, or a LINQ to JET/OLEDB provider.
Out of the box, MS doesn't make one. There may be a 3rd party who does.
Actually I recently (today) discovered that you can access an Access database with LinqToSql. It must be in the 2002 or newer format, you will not be able to drag and drop the tables to your datacontext so either manually create the objects in your dbml or you can use SQL Server Migration for Access to move it to a sql server and then drag and drop all you want. When you want to actually create the context pass it an OleDbConnection. Use your standard Jet.OLEDB.4.0 connection string on the OleDbConnection and you are good to go. Not sure of the limitation this may incurr though. I just did a quick sample and did an OrderBy without issue.
I wrote a small sample program to test this out with David's answer. You'll need to make an access database and manually create the DBML for Linq-to-SQL, as you cannot drag 'n drop them.
Inserts fail, citing Missing semicolon (;) at end of SQL statement. but queries seem to work alright.
using System;
using System.Collections.Generic;
using System.Data.OleDb;
using System.IO;
using System.Linq;
using Linq2Access.Data;
namespace Linq2Access
{
class Program
{
static readonly string AppPath = Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location);
static readonly string DbPath = Path.Combine(AppPath, "Data", "database.accdb");
static readonly string DbConnString = #"Provider=Microsoft.ACE.OLEDB.12.0;Data Source='" + DbPath + "';Persist Security Info=False;";
static void Main(string[] args)
{
if (!File.Exists(DbPath))
throw new Exception("Database file does not exist!");
using (OleDbConnection connection = new OleDbConnection(DbConnString))
using (DataRepositoryDataContext db = new DataRepositoryDataContext(connection))
{
List<dbProject> projects = new List<dbProject>();
for (int i = 1; i <= 10; i++)
{
dbProject p = new dbProject() { Title = "Project #" + i };
for (int j = 1; j <= 10; j++)
{
dbTask t = new dbTask() { Title = "Task #" + (i * j) };
p.dbTasks.Add(t);
}
projects.Add(p);
}
try
{
//This will fail to submit
db.dbProjects.InsertAllOnSubmit(projects);
db.SubmitChanges();
Console.WriteLine("Write succeeded! {0} projects, {1} tasks inserted",
projects.Count,
projects.Sum(x => x.dbTasks.Count));
}
catch(Exception ex)
{
Console.WriteLine("Write FAILED. Details:");
Console.WriteLine(ex);
Console.WriteLine();
}
try
{
//However, if you create the items manually in Access they seem to query fine
var projectsFromDb = db.dbProjects.Where(x => x.Title.Contains("#1"))
.OrderBy(x => x.ProjectID)
.ToList();
Console.WriteLine("Query succeeded! {0} Projects, {1} Tasks",
projectsFromDb.Count,
projectsFromDb.Sum(x => x.dbTasks.Count));
}
catch (Exception ex)
{
Console.WriteLine("Query FAILED. Details:");
Console.WriteLine(ex);
Console.WriteLine();
}
Console.WriteLine();
Console.WriteLine("Press any key to continue...");
Console.ReadKey();
}
}
}
}
You can use a DataSet. There are linq extensions that will allow you to query the data with all that LINQ goodness we have become use to :)
eICATDataSet.ICSWSbuDataTable tbl = new eICATDataSet.ICSWSbuDataTable();
ICSWSbuTableAdapter ta = new ICSWSbuTableAdapter();
ta.Fill(tbl);
var res = tbl.Select(x => x.ProcedureDate.Year == 2010);
I have seen this question a lot and in several fora. I made a go at it and here is a complete answer for those who have been looking at it.
LinQ was not made for Access. However, many of the queries will work with Access, including delete procedure. So, according to me, there are only 2 crucial deficiencies when working with Access, which are:
not being able to save data.
not being able to drag and drop objects onto the dbml
Insert will fail with the error "missing semicolon (;)". This is because LinQ save procedure was made to save data and retrieve the primary key ID of the record saved in one go. We know that you cannot execute multiple SQL statements in Access, so that is the reason for that failure.
Update will fail with the error "record not found". An update procedure will of cause look for the record to be updated then update it. I cannot tell why it wouldn't find it, when normal LinQ query to find a record works fine.
Because there is so much benefit to use LinQ, I figured out how to work around the deficiency, while enjoy the other benefits throughout my application. This is how (NB: My codes are in VB.net, but you can convert if required):
Create the LinQ to SQL (.dbml) class to manage your LinQ against the access database, and a way to manager your save procedure. Below is the full procedures of what I created and I now work with LinQ to Access without any problems:
Add a DataGridView on a form. Add buttons for Add, Edit & Delete
Code to fill the grid:
Private Sub ResetForm()
Try
Using db As New AccessDataClassesDataContext(ACCCon)
Dim rows = (From row In db.AccountTypes
Where row.AccountTypeID > 1
Order By row.AccountTypeID Ascending
Select row).ToList()
Me.DataGridView1.DataSource = rows
End Using
Catch ex As Exception
MessageBox.Show("Error: " & vbCr & ex.ToString, "Data Error", MessageBoxButtons.OK)
End Try
End Sub
DetailForm
Code to set control values
Private Sub ResetForm()
Try
If _accountTypeID = 0 Then
Exit Sub
End If
Using db As New AccessDataClassesDataContext(ACCCon)
'Dim rows = (From row In db.AccountTypes
' Where row.AccountTypeID = _accountTypeID
' Order By row.AccountTypeID Ascending
' Select row.AccountTypeID, row.AccountType, row.LastUpdated).ToList()
Dim rows = (From row In db.AccountTypes
Where row.AccountTypeID = _accountTypeID
Select row).ToList()
For Each s In rows
Me.AccountTypeIDTextBox.Text = s.AccountTypeID
Me.myGuidTextBox.Text = s.myGuid
Me.AccountTypeTextBox.Text = s.AccountType
Me.AcHeadIDTextBox.Text = s.AcHeadID
Me.DescriptionTextBox.Text = s.Description
Me.LastUpdatedDateTimePicker.Value = s.LastUpdated
Next
End Using
Catch ex As Exception
End Try
End Sub
LinQToSQLClass
You will have to add the data objects to the dbml manually since you cannot drag and drop when using Access. Also note that you will have to set all the properties of the fields correctly in the properties windows. Several properties are not set when you add the fields.
Code to Save
Public Function SaveAccountType(Optional ByVal type As String =
"Close") As Boolean
Dim success As Boolean = False
Dim row As New AccountType
Using db As New AccessDataClassesDataContext(ACCCon)
If _accountTypeID > 0 Then
row = (From r In db.AccountTypes
Where r.AccountTypeID = _accountTypeID).ToList()(0)
If String.IsNullOrEmpty(row.AccountTypeID) Then
MessageBox.Show("Requested record not found", "Update Customer Error")
Return success
End If
End If
Try
With row
.myGuid = Me.myGuidTextBox.Text
.AccountType = Me.AccountTypeTextBox.Text
.Description = Me.DescriptionTextBox.Text
.AcHeadID = Me.AcHeadIDTextBox.Text
.LastUpdated = Date.Parse(Date.Now())
End With
If _accountTypeID = 0 Then db.AccountTypes.InsertOnSubmit(row)
db.SubmitChanges()
success = True
Catch ex As Exception
MessageBox.Show("Error saving to Customer: " & vbCr & ex.ToString, "Save Data Error")
End Try
End Using
Return success
End Function
Now replace these two lines:
If _accountTypeID = 0 Then db.AccountTypes.InsertOnSubmit(row)
db.SubmitChanges()
with something like this:
Dim cmd As IDbCommand
cmd = Me.Connection.CreateCommand()
cmd.Transaction = Me.Transaction
cmd.CommandText = query
If myGuid.Trim.Length < 36 Then myGuid = UCase(System.Guid.NewGuid.ToString())
cmd.Parameters.Add(New OleDbParameter("myGuid", row.myGuid))
cmd.Parameters.Add(New OleDbParameter("AccountType", row.AccountType))
cmd.Parameters.Add(New OleDbParameter("Description", row.Description))
cmd.Parameters.Add(New OleDbParameter("AcHeadID", row.AcHeadID))
cmd.Parameters.Add(New OleDbParameter("LastUpdated", Date.Now))
If AccountTypeID > 0 Then cmd.Parameters.Add(New OleDbParameter("AccountTypeID", row.AccountTypeID))
If Connection.State = ConnectionState.Closed Then Connection.Open()
result = cmd.ExecuteNonQuery()
cmd = Me.Connection.CreateCommand()
cmd.Transaction = Me.Transaction
cmd.CommandText = "SELECT ##IDENTITY"
result = Convert.ToInt32(cmd.ExecuteScalar())
The last part of the code above is what gets you the ID of the record saved. Personally, I usually make that an option, because I don't need it in most of the cases, so I don't need to add that overhead of fetching back data every time a record is saved, I am happy just to know a record was saved.
That is the overhead added to LinQ, which causes Insert to fail with Access. Is it really necessary to have it? I don't think so.
You may have noted that I normally put my Update and Insert procedures together, so that saves me time and has address both the Insert & Update procedures in one go.
Code for Delete:
Private Sub DelButton_Click(sender As Object, e As EventArgs) Handles DelButton.Click
Using db As New AccessDataClassesDataContext(ACCCon)
Dim AccountTypeID As Integer = Me.DataGridView1.CurrentRow.Cells(0).Value
Dim row = From r In db.AccountTypes Where r.AccountTypeID = AccountTypeID
For Each detail In row
db.AccountTypes.DeleteOnSubmit(detail)
Next
Try
db.SubmitChanges()
Catch ex As Exception
' Provide for exceptions.
MsgBox(ex)
End Try
End Using
End Sub
Now you can enjoy LinQ to Access! Happy coding :)
LINQ to SQL only works for SQL Server databases. What you need is the Microsoft Entity Framework. This makes object oriented access to your mdb. From this you can run LINQ queries.
http://msdn.microsoft.com/en-us/library/aa697427(vs.80).aspx
Hopefully this is not a ServerFault question...
I'm working forward on migrating a project from storing data in XML Serialization to a MySQL database. I'm using the example provided me from a previous question answered yesterday.
Connecting using phpMyAdmin and MySQL Workbench I've created a Stored Procedure called 'sprocOrderSelectSingleItem'. It seems to work well with MySQL for all I can tell. When I run the SHOW CREATE PROCEDURE sprocOrderSelectSingleItem it returns the following:
CREATE DEFINER=username#% PROCEDURE sprocOrderSelectSingleItem(IN orderID INTEGER)
BEGIN SELECT * FROM tblOrders WHERE ID=orderID; END
My cooperative ASP.NET code goes something like this:
public static Order GetItem(int ID)
{
Order objOrder = null;
using (OdbcConnection objConnection = new OdbcConnection(Utils.ApplicationConfiguration.ConnectionString))
{
OdbcCommand objCommand = new OdbcCommand("sprocOrderSelectSingleItem", objConnection);
objCommand.CommandType = CommandType.StoredProcedure;
objCommand.Parameters.AddWithValue("orderID", ID);
objConnection.Open();
using (OdbcDataReader objReader = objCommand.ExecuteReader())
{
if (objReader.Read())
{
objOrder = FillDataRecord(objReader);
}
objReader.Close();
}
objConnection.Close();
}
return objOrder;
}
When I view the page I get the following error message:
ERROR [42000] [MySQL][ODBC 5.1 Driver][mysqld-5.0.77]You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'sprocOrderSelectSingleItem' at line 1
Really not catching on to what could be missing or going wrong. Are there any additional tests I should/could be running to confirm things are working on the MySQL side? Am I missing a step to pass the Stored Procedure call correctly in ASP.NET? The code breaks at the line of:
using (OdbcDataReader objReader = objCommand.ExecuteReader())
Replacing the line of
OdbcCommand objCommand = new OdbcCommand("sprocOrderSelectSingleItem", objConnection);
with this instead
OdbcCommand objCommand = new OdbcCommand("SELECT * FROM tblOrders WHERE ID=" + ID + ";", objConnection);
and everything works as expected.
Thanks for any help you guys can provide.
Your can run an execute on sprocOrderSelectSingleItem in Mysql directly with the ID parameter.
It will show that your StoredProc run correctly.
Here is a sample code in C# that call a stored proc.
OdbcCommand salesCMD = new OdbcCommand("{ CALL SalesByCategory(?) }", nwindConn);
salesCMD.CommandType = CommandType.StoredProcedure;
OdbcParameter myParm = salesCMD.Parameters.Add("#CategoryName", OdbcType.VarChar, 15);
myParm.Value = "Beverages";
OdbcDataReader myReader = salesCMD.ExecuteReader();
Look at the "Call" in the OdbcCommand and the "?" for the parameter that is later supplied with a value.
Can you try something like below:
OdbcCommand cmd = new OdbcCommand();
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = "{call LoadCustCliOrders(?,?,?,?)}";
cmd.Parameters.Add("CUST_ID",OdbcType.Int);
cmd.Parameters.Add("CLIENT_ID",OdbcType.Int);
cmd.Parameters.Add("DATE_FROM",OdbcType.Date);
cmd.Parameters.Add("DATE_TO",OdbcType.Date);
...
cmd.Parameters["CUST_ID"].Value = _CustId;
cmd.Parameters["CLIENT_ID"].Value = _ClientId;
cmd.Parameters["DATE_FROM"].Value = _DateFrom;
cmd.Parameters["DATE_TO"].Value = _DateTo;
cmd.ExecuteReader
Are you sure that you are using the same username or user with the same access privileges.
I think you need to add the word "CALL" before the stored proc.
It should be CALL sprocOrderSelectSingleItem and try.
Suppose I am calling a query "SELECT name, city, country FROM People". Once I execute my SqlDataReader do columns come in the same order as in my sql query?
In other words can I rely that the following code will always work correctly:
SqlConnection connection = new SqlConnection(MyConnectionString);
SqlCommand command = new SqlCommand();
command.Connection = connection;
command.CommandText = "SELECT [name], [city], [country] WHERE [id] = #id";
try
{
connection.Open();
SqlDataReader reader = command.ExecuteReader(System.Data.CommandBehavior.SingleRow);
if (reader.Read())
{
// Read values.
name = reader[0].ToString();
city = reader[1].ToString();
country = reader[2].ToString();
}
}
catch (Exception)
{
throw;
}
finally
{
connection.Close();
}
Also how much performance do I lose if I use column names instead of ordinals (reader["name"])?
Are there any official microsoft documents describing the behavior of column ordering in SqlDataReader?
Yes they do but you can also use SqlDataReader.GetName(ordinal) and SqlDataReader.GetOrdinal(name).
As for performance, I think it's probably extremely insignificant compared to the overhead of say, retrieving the next row of data.
I totally agree with Josh - the positions of the fields are indeed such as you specify them in your SQL query text.
BUT: I would still prefer to use the column names, since it's more robust. E.g. what if you need to add a field to your SQL query?
command.CommandText = "SELECT [name], [jobtitle], [city], [country] WHERE [id] = #id";
Now suddenly you have to rewrite all your code to change the positions....
What I normally do outside the loop that enumerates through all the rows returned by the data reader is determine the positions of each field I'm interested in:
int namePosition = reader.GetOrdinal("name");
int cityPosition = reader.GetOrdinal("city");
and then I use these positions inside my loop handling the data to get quick access to the individual fields. That way you determine the positions only once, but you're using positions in your looping over the data - the best of both worlds! :-)
Marc
This example is the most maintainable and easiest to read:
int? quantity = reader.Get<int?>("Quantity");
Guid token = reader.Get<Guid>("Token");
It relies on the following extension method I created. It performs DB null checks, provides an informative error message when field is not found, and does not break when columns are re-aligned.
internal static T Get<T>(this SqlDataReader reader, string fieldName)
{
int ordinal;
try
{
ordinal = reader.GetOrdinal(fieldName);
}
catch (IndexOutOfRangeException)
{
throw new IndexOutOfRangeException(string.Format("Field name '{0}' not found.", fieldName));
}
return !reader.IsDBNull(ordinal) ? (T)reader.GetValue(ordinal) : default(T);
}