Develop Reference

how to create mysql update query for updating multiple rows in in one statement for c#.net windows applicaiton

How to write mysql update query for updating multiple rows of datagridview in single statement by passing parameters and then executing all together in c#.net windows application
for example create update query like is given below
foreach(DatagridViewRow dr in datagridview)
{
sql = "update table1 set name=#name where id=#id; update table1 set name=#name where id=#id; update table1 set name=#name where id=#id;"
}
How to create a sql query with parameters? So that after creation of query; we can execute it together to make changes in multiple rows.

You don't need to put multiple Update queries together.
Here take a look:
string sql = "update table1 set name=#name where id=#id";
MySqlParameter pId = new MySqlParameter("#id", SqlDbType.BigInt);
MySqlParameter pName = new MySqlParameter("#name", SqlDbType.NVarchar);
cmd.Parameters.Clear();
cmd.CommandText = query;
cmd.Parameters.Add(pName);
cmd.Parameters.Add(pId);
foreach(DatagridViewRow dr in datagridview)
{
pId.Value = dr.Rows["iDColumn"].ToString();
pName.Value = dr.Rows["nameColumn"].ToString();
cmd.ExecuteNonQuery();
}
Hope this helps.

C# ComboBox Select Error: "Incorrect Syntax Near '.'"

Note: my office doesn't allow me to view YouTube and several other sites that probably have the answer to this question on them (they are blocked), which is why Googling the answer hasn't yielded results.
ComboBox code reference: found here
On my C# Form, I have filled a ComboBox with tables from a database (see below code), which returns the appropriate values and functions correctly:
public Form1()
{
InitializeComponent();
// Connection
SqlConnection conn = new SqlConnection();
conn.ConnectionString = "CONNECTION STRING" // shortened for security and convenience
// Fill ComboBox with SQL Values
conn.Open();
SqlCommand cmbTables = new SqlCommand("SELECT name FROM sys.tables", conn);
SqlDataReader read = cmbTables.ExecuteReader();
DataTable cmbData = new DataTable();
cmbData.Columns.Add("name", typeof(string));
cmbData.Load(read);
cmb1.DisplayMember = "name";
cmb1.DataSource = cmbData;
conn.Close();
}
After the ComboBox loads the tables (which works), the application then selects a table and clicks a button that loads the table, which is selected. This is where the code errors:
private void button1_Click(object sender, EventArgs e)
{
using (var connection = Utilities.GetConnection())
{
string table = Convert.ToString(txt1.Text);
string cmb1Value = Convert.ToString(cmb1.SelectedItem);
// Stored Procedure
SqlCommand select = new SqlCommand("EXECUTE STOREDPROCEDURE" + cmb1Value, connection); // shortened for security and convenience
select.Parameters.Add(new SqlParameter(cmb1Value, table));
// Data View
SqlDataAdapter ad= new SqlDataAdapter(select);
ad.SelectCommand = select;
DataTable dt = new DataTable();
ad.Fill(dt); // this generates the error "Incorrect Syntax Near '.'"
BindingSource b = new BindingSource();
b.DataSource = dt;
dGrid.DataSource = b;
ad.Update(dt);
connection.Close();
}
}
Even though the ComboBox loads the appropriate values, from the above code, I may be missing something which attaches those values to the SELECT stored procedure (all it does is call SELECT statement through a variable passed to it). The error, "Incorrect Syntax Near '.'" looks like a SQL Server error that I've seen, but can't remember how I generate it (this is how I usually troubeshoot where the TSQL code went wrong).\
Stored Procedure Related code:
C#:
SqlCommand select = new SqlCommand("EXECUTE STOREDPROCEDURE " + cmb1Value, connection);
TSQL:
CREATE PROCEDURE [STOREDPROCEDURE]
#TableName VARCHAR(250)
AS
BEGIN
DECLARE #sql NVARCHAR(MAX)
SET #sql = N'SELECT TOP 100 *
FROM ' + #TableName
EXECUTE(#sql)
END
-- Note this works in SSMS without a problem.
The above code is incorrect, and when I tweak the TSQL code, I generate similar errors, telling me that somewhere I am missing a conversion, or another variable because SQL Server isn't seeing these table values returned by the SELECT (first block of code). I can ascertain this because I have a second ComboBox that uses similar code EXCEPT that I populated the ComboBox with manual values, and it connects to the tables in the database with no error. So, the ComboBox, which grabs values from the database, that you see above, does not function correctly.
For instance, if I only add the below line of code to the code, I receive an error that it can't find the database "EXECUTE STOREDPROCEDURE System'
select.CommandType = CommandType.StoredProcedure;
However, System isn't a part of anything, so where did that come from? It never errored with this code on the manual ComboBox, as it had no trouble finding the database (using the same connection string, server and database!).
If I try to use a TSQL parameter, such as:
SqlCommand select = new SqlCommand("EXECUTE stp_ReturnTable #p", scon);
select.Parameters.Add(new SqlParameter("#p", cmb1Value));
Suddenly, it can't find the stored procedure. Again, the connection strings are identical for the manual ComboBox and the dynamic ComboBox.
I think the code behind the dynamic ComboBox is wrong. When I'm out of the office, I'll review some videos with detailed demonstrations on how to create a dynamic ComboBox from a database and I have a hunch that a system object is in the way (based on the System error, which exists nowhere in my code, as well as it suddenly being unable to find the database or procedure).

The missing key point in your code is the CommandType.
Without the proper set of this property the default is CommandText and thus the Framework expects a statement that starts with SELECT/INSERT/UPDATE/DELETE etc....
using (var connection = Utilities.GetConnection())
{
string table = Convert.ToString(txt1.Text);
string cmb1Value = Convert.ToString(cmb1.SelectedItem);
// Stored Procedure
SqlCommand select = new SqlCommand("STOREDPROCEDURE", connection);
select.Parameters.Add(new SqlParameter("#TableName", cmb1Value));
// That's the key to let ADO.NET accept the previous CommandText as valid.
// If you omit this the CommandText is assumed to be a SELECT/UPDATE/DELETE etc..
select.CommandType = CommandType.StoredProcedure;
// Data View
SqlDataAdapter ad= new SqlDataAdapter(select);
DataTable dt = new DataTable();
ad.Fill(dt);
BindingSource b = new BindingSource();
b.DataSource = dt;
dGrid.DataSource = b;
}
EDIT Having seen the code of the SP then you could simply set the SqlParameter name to the constant #TableName and pass the value extracted from the combobox as the value to be used inside the SP
EDIT I have looked again at your code and I suspect that the culprit is the line
string cmb1Value = Convert.ToString(cmb1.SelectedItem);
Looking at how you have filled your combo, this line, doesn't return the tablename as you expect, but the generic string System.Data.DataRowView because the DataSource of the combo is a DataTable and not a string collection. You should try to change that line in this way
DataRowView rw = cmb1.SelectedItem as DataRowView;
if(rw != null)
{
string cmbValue1 = rw["name"].ToString();
....
And yes, your code should work also without the CommandType.StoredProcedure line because the text EXECUTE sp param is recognized as a valid sql commandtext (but why do you use it when a direct call to the storedprocedure could be optimized for reuse?)

C#- Updating just updated column(s)

I have a web form. There are 20 fields that correspond to the columns in a database table. Let's say there's one record that has a BIRTHDATE column and I change its value from 13-July-2000 to 12-FEB-1985. But I don't touch the rest of the columns. Is there a way in C# to run an update statement like this:
UPDATE TABLE1 SET BIRHDATE=NEWVALUE WHERE ID=1111
instead of updating all the columns of the row like this:
UPDATE TABLE1 SET COLUMN1=NEWVALUE1, COLUMN2=NEWVALUE2,......,BIRTHDATE=NEWVALU
I think it would be a waste of resource. Am I wrong? I think DataAdapters are for this purpose but I'm not sure.

You can send a direct update statement to the Oracle Engine in this way.
using (OracleConnection cnn = new OracleConnection(connString))
using (OracleCommand cmd = new OracleCommand("UPDATE TABLE1 SET BIRHDATE=:NewDate WHERE ID=:ID", cnn))
{
cmd.Parameters.AddWithValue(":NewDate", YourDateTimeValue);
cmd.Parameters.AddWithValue(":ID", 111);
cnn.Open();
cmd.ExecuteNonQuery();
}
EDIT:
If you don't know which fields are changed (and don't want to use a ORM Tool) then you need to keep the original DataSource (a datatable, dataset?) used to populate initially your fields. Then update the related row and use a OracleDataAdapter.
using(OracleConnection cnn = new OracleConnection(connString))
using (OracleCommand cmd = new OracleCommand("SELECT * FROM TABLE1 WHERE 1=0", cnn))
{
OracleAdapter adp = new OracleDataAdapter();
adp.SelectCommand = cmd;
// The OracleDataAdapter will build the required string for the update command
// and will act on the rows inside the datatable who have the
// RowState = RowState.Changed Or Inserted Or Deleted
adp.Update(yourDataTable);
}
Keep in mind that this approach is inefficient because it requires two trip to the database. The first to discover your table structure, the second to update the row/s changed. Moreover, for the OracleDataAdapter to prepare the UpdateCommand/InsertCommand/DeleteCommand required, it needs a primary key in your table.
On the contrary, this is handy if you have many rows to update.
The last alternative (and probably the fastest) is a StoredProcedure, but in this case you need to go back to my first example and adapt the OracleCommand to use a StoredProcedure, (Add all fields as parameters, change CommandType to CommandType.StoredProcedure and change the text of the command to be the name of the StoredProcedure). Then the StoredProcedure will choose which fields need to be updated.

How to use auto indexing in ACCESS database using OleDb in C# with sql commands

I wrote a form based program in C# that uses MS access database to store its data.
In the MDB file I have a single table named __item__
in the table there are 7 fields of which the first one is called __item_id__ and it is the auto indexer of the table, so when I add new entry it should auto increase each time, so I won't have 2 entry's with the same id.
In the program I use the following code (this isn't the full code, just the relevant one):
using System.Data.OleDb;
private OleDbConnection con; // create connection
private OleDbCommand cmd; // create command
con = new OleDbConnection("Provider = Microsoft.Jet.OLEDB.4.0; Data Source = d:\\library0.1\\DB.mdb");
cmd = new OleDbCommand();
cmd.Connection = con;
cmd.CommandText = "INSERT INTO Item VALUES (#item_name, #creator_name,#publishing_name,#item_type,#genre,#year_publication);";
con.Open(); // open the connection
cmd.ExecuteNonQuery();
con.Close();
this code will give me an error __ExecuteNonQuery__ claiming I have too few fields.
It wants me to enter the __item_id__ manually, like this:
cmd.CommandText = "INSERT INTO Item VALUES (#item_id, #item_name, #creator_name,#publishing_name,#item_type,#genre,#year_publication);";
How can I avoid manual input and have the program auto index the item_id for each new entry?

If you use INSERT INTO without specifying the column list you should provide parameter for all columns.
To avoid the error change your commandtext to:
"INSERT INTO Item " +
"(item_name, creator_name publishing_name, item_type, genre, year_publication) " +
"VALUES " +
"(#item_name, #creator_name,#publishing_name,#item_type,#genre,#year_publication);";

Using temporary table in c#

I read an excel sheet into a datagrid.From there , I have managed to read the grid's rows into a DataTable object.The DataTable object has data because when I make equal a grid's datasource to that table object , the grid is populated.
My Problem : I want to use the table object and manipulate its values using SQL server,(i.e. I want to store it as a temporary table and manipulate it using SQL queries from within C# code and , I want it to return a different result inte a grid.(I don't know how to work with temporary tables in C#)
Here's code to execute when clicking button....
SqlConnection conn = new SqlConnection("server = localhost;integrated security = SSPI");
//is connection string incorrect?
SqlCommand cmd = new SqlCommand();
//!!The method ConvertFPSheetDataTable Returns a DataTable object//
cmd.Parameters.AddWithValue("#table",ConvertFPSheetDataTable(12,false,fpSpread2_Sheet1));
//I am trying to create temporary table
//Here , I do a query
cmd.CommandText = "Select col1,col2,SUM(col7) From #table group by col1,col2 Drop #table";
SqlDataAdapter da = new SqlDataAdapter(cmd.CommandText,conn);
DataTable dt = new DataTable();
da.Fill(dt); ***// I get an error here 'Invalid object name '#table'.'***
fpDataSet_Sheet1.DataSource = dt;
//**NOTE:** fpDataSet_Sheet1 is the grid control

Change your temp table from #table to ##table in both places.
Using ## means a global temp table that stays around. You'll need to Drop it after you have completed your task.
Command = " Drop Table ##table"

Putting the data into a database will take time - since you already have it in memory, perhaps LINQ-to-Objects (with DataSetExtensions) is your friend? Replace <int> etc with the correct types...
var query = from row in table.Rows.Cast<DataRow>()
group row by new
{
Col1 = row.Field<int>(1),
Col2 = row.Field<int>(2)
} into grp
select new
{
Col1 = grp.Key.Col1,
Col2 = grp.Key.Col2,
SumCol7 = grp.Sum(x => x.Field<int>(7))
};
foreach (var item in query)
{
Console.WriteLine("{0},{1}: {2}",
item.Col1, item.Col2, item.SumCol7);
}

I don't think you can make a temp table in SQL the way you are thinking, since it only exists within the scope of the query/stored procedure that creates it.
If the spreadsheet is a standard format - meaning you know the columns and they are always the same, you would want to create a Table in SQL to put this file into. There is a very fast way to do this called SqlBulkCopy
// Load the reports in bulk
SqlBulkCopy bulkCopy = new SqlBulkCopy(connectionString);
// Map the columns
foreach(DataColumn col in dataTable.Columns)
bulkCopy.ColumnMappings.Add(col.ColumnName, col.ColumnName);
bulkCopy.DestinationTableName = "SQLTempTable";
bulkCopy.WriteToServer(dataTable);
But, if I'm understanding your problem correctly, you don't need to use SQL server to modify the data in the DataTable. You c an use the JET engine to grab the data for you.
// For CSV
connStr = string.Format("Provider=Microsoft.JET.OLEDB.4.0;Data Source={0};Extended Properties='Text;HDR=Yes;FMT=Delimited;IMEX=1'", Folder);
cmdStr = string.Format("SELECT * FROM [{0}]", FileName);
// For XLS
connStr = string.Format("Provider=Microsoft.JET.OLEDB.4.0;Data Source={0}{1};Extended Properties='Excel 8.0;HDR=Yes;IMEX=1'", Folder, FileName);
cmdStr = "select * from [Sheet1$]";
OleDbConnection oConn = new OleDbConnection(connStr);
OleDbCommand cmd = new OleDbCommand(cmdStr, oConn);
OleDbDataAdapter da = new OleDbDataAdapter(cmd);
oConn.Open();
da.Fill(dataTable);
oConn.Close();
Also, in your code you ask if your connection string is correct. I don't think it is (but I could be wrong). If yours isn't working try this.
connectionString="Data Source=localhost\<instance>;database=<yourDataBase>;Integrated Security=SSPI" providerName="System.Data.SqlClient"

Pardon me, if I have not understood what you exactly want.
If you want to perform SQL query on excel sheet, you could do it directly.
Alternatively, you can use SQL Server to query excel (OPENROWSET or a function which I dont remember right away). Using this, you can join a sql server table with excel sheet
Marc's suggestion is one more way to look at it.

Perhaps you could use a DataView. You create that from a DataTable, which you already have.
dv = new DataView(dataTableName);
Then, you can filter (apply a SQL WHERE clause) or sort the data using the DataView's methods. You can also use Find to find a matching row, or FindRows to find all matching rows.
Some filters:
dv.RowFilter = "Country = 'USA'";
dv.RowFilter = "EmployeeID >5 AND Birthdate < #1/31/82#"
dv.RowFilter = "Description LIKE '*product*'"
dv.RowFilter = "employeeID IN (2,4,5)"
Sorting:
dv.Sort = "City"
Finding a row: Find the customer named "John Smith".
vals(0)= "John"
vals(1) = "Smith"
i = dv.Find(vals)
where i is the index of the row containing the customer.
Once you've applied these to the DataView, you can bind your grid to the DataView.

Change the command text from
Select col1,col2,SUM(col7) From #table group by col1,col2
to
Select col1,col2,SUM(col7) From ##table group by col1,col2