How can I know whether the table in database is affected after these instructions? I try to show the query result in console but it doesn't show anything.
static void Main(string[] args)
{
DateTime date = new DateTime(2013, 3, 4);
try
{
SqlConnection connection = new SqlConnection("Data Source=ExchangeRatesByDate/TestApplication/Rates_DB.sdf");
Console.WriteLine("Connection is created");
connection.Open();
Console.WriteLine("Connection is opened");
SqlCommand insertCommand = connection.CreateCommand();
insertCommand.CommandText = "INSERT INTO Rates_Table(ISO, Amount, Rate, Date) VALUES (USD, 1, 417.5, date)";
insertCommand.ExecuteNonQuery();
SqlDataAdapter adapter = new SqlDataAdapter("SELECT * FROM Rates_Table", connection);
DataTable data = new DataTable();
adapter.Fill(data);
Console.WriteLine(adapter);
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
ExecuteNonQuery() returns an integer showing number of affected rows. ExecuteNonQuery
You can use the ExecuteNonQuery to perform catalog operations (for
example, querying the structure of a database or creating database
objects such as tables), or to change the data in a database without
using a DataSet by executing UPDATE, INSERT, or DELETE statements.
Although the ExecuteNonQuery returns no rows, any output parameters or
return values mapped to parameters are populated with data.
For UPDATE, INSERT, and DELETE statements, the return value is the
number of rows affected by the command. When a trigger exists on a
table being inserted or updated, the return value includes the number
of rows affected by both the insert or update operation and the number
of rows affected by the trigger or triggers. For all other types of
statements, the return value is -1. If a rollback occurs, the return
value is also -1.
try like this
int updatedRows = insertCommand.ExecuteNonQuery();
if(updatedRows>0)
{
//do something
}
i think u are showing SqlDataAdapter object show to datatable ,and also use parameter for the insert string like 'USD'
the ExecuteNonQuery() returns an integer for the number of affected records.
int _affected = insertCommand.ExecuteNonQuery();
ExecuteNonQuery()
follow-up question
INSERT INTO Rates_Table(ISO, Amount, Rate, Date) VALUES (USD, 1, 417.5, date)
in the statement above, are values USD and date are real values because if so, it pretty sure it will thrown an exception. It should be wrap with single quotes like this:
INSERT INTO Rates_Table(ISO, Amount, Rate, Date) VALUES ('USD', 1, 417.5, '')
because they are string literals. But it's not the proper way to insert data with real values in the INSERT statement. The values should be parameterized to avoid sql injection.
string sqlStatement = "INSERT INTO Rates_Table(ISO, Amount, Rate, Date) VALUES (#iso, #Amount, #rate, #date)";
using (SqlConnection conn = new SqlConnection(connStr))
{
using(SqlCommand comm = new SqlCommand())
{
comm.Connection = conn;
comm.CommandText = sqlStatement;
comm.CommandType = CommandType.Text;
comm.Parameters.AddWithValue("#iso", '-- value --');
comm.Parameters.AddWithValue("#Amount", '-- value --');
comm.Parameters.AddWithValue("#rate", '-- value --');
comm.Parameters.AddWithValue("#date", '-- value --');
try
{
conn.Open();
int _affected = comm.ExecuteNonQuery();
}
catch(SqlException e)
{
// do something with the exception
// do not hide it
// e.Message.ToString()
}
}
}
For proper coding
use using statement for propr object disposal
use try-catch block to properly handle objects
Related
I have data in Database table:
Here is the method for adding data:
public static void AddRecordToDatatable(string WindowTitle, int TimeSpent,
DateTime DateToday, string Project, string Username)
{
string sql = #"INSERT INTO dbo.Log (WindowTitle,TimeSpent,DateToday,Project,Username)" +
" VALUES (#WindowTitle,#TimeSpent,#DateToday,#Project,#Username)";
// Create the connection (and be sure to dispose it at the end)
using (SqlConnection cnn = new SqlConnection(DBconnectionString))
{
try
{
// Open the connection to the database.
// This is the first critical step in the process.
// If we cannot reach the db then we have connectivity problems
cnn.Open();
// Prepare the command to be executed on the db
using (SqlCommand cmd = new SqlCommand(sql, cnn))
{
// Create and set the parameters values
cmd.Parameters.Add("#WindowTitle", SqlDbType.NVarChar).Value = WindowTitle;
cmd.Parameters.Add("#TimeSpent", SqlDbType.Int).Value = TimeSpent;
cmd.Parameters.Add("#DateToday", SqlDbType.DateTime).Value = DateTime.Now.Date;
cmd.Parameters.Add("#Project", SqlDbType.NVarChar).Value = Project;
cmd.Parameters.Add("#Username", SqlDbType.NVarChar).Value = Username;
// Let's ask the db to execute the query
int rowsAdded = cmd.ExecuteNonQuery();
if (rowsAdded > 0)
{
//MessageBox.Show("Row inserted");
}
else
{
// This should never really happen, but let's leave it here
//MessageBox.Show("No row inserted");
}
}
cnn.Close();
}
catch (Exception ex)
{
// We should log the error somewhere,
// for this example let's just show a message
MessageBox.Show("ERROR:" + ex.Message);
}
}
}
How it is possible to check for existing record before inputting data to Database table and sum on certain value if it exists?
So basically check if WindowTitle = WindowTitle and DateToday = DateToday, if these two match, then take TimeSpent and sum it to existing TimeSpent in Database Table without inputting a new row.
I have tried to test ON DUPLICATE KEY UPDATE WindowTitle = #WindowTitle, DateToday = #DateToday after INSERT but Visual Studio is giving an error in Debugger for such a command pointing to ON (Incorrect syntax near ON). Also I am not sure if ON DUPLICATE is the best approach for this kind of case.
You need to expand your SQL to check for the existence of the record you think could exist.
IF EXISTS (SELECT 1 FROM dbo.Log WHERE WindowTitle = #WindowTitle AND DateToday = #DateToday)
BEGIN
--UPDATE HERE
END
ELSE
BEGIN
-- INSERT HERE
END
Alternatively you can create a query method and call that first, before calling AddRecordToDatatable
Personally I would do all of these CRUD operations using an ORM such as EF Core or preferably, NHibernate. But this all depends on requirements, limitations etc.
For some reason, ExecuteNonQuery() in C# returns -1, though when I run a query separately, the value returns the actual value needed.
For Example:
try
{
var connString ="Data Source=ServerName;InitialCatalog=DatabaseName;Integrated Security=true;"
SqlConnection conn = new SqlConnection(connString);
SqlCommand someCmd = new SqlCommand("SELECT COUNT(*) FROM SomeTable");
someCmd.Connection = conn;
conn.Open();
var theCount = cmd.ExecuteNonQuery();
conn.Close();
}
catch(Exception ex)
{
Console.WriteLine(ex.Message);
}
When the command is executed it returns -1. Though if run the query separately,
SELECT COUNT(*) FROM SomeTable;
Column returns one row with a count of 4 if that table being queried has 4 rows.
Based on MSDN:
For UPDATE, INSERT, and DELETE statements, the return value is the number of rows affected by the command. When a trigger exists on a table being inserted or updated, the return value includes the number of rows affected by both the insert or update operation and the number of rows affected by the trigger or triggers. For all other types of statements, the return value is -1. If a rollback occurs, the return value is also -1.
You want to return the number of rows affected by the command and save it to an int variable but since the type of statement is select so it returns -1.
Solution: If you want to get the number of rows affected by the SELECT command and save it to an int variable you can use ExecuteScalar.
var theCount = (int)cmd.ExecuteScalar();
You can use Ef core with Ado.net like this example
var context = new SampleDbContext();
using (var connection = context.Database.GetDbConnection())
{
connection.Open();
using (var command = connection.CreateCommand())
{
command.CommandText = "SELECT COUNT(*) FROM SomeTable";
var result = command.ExecuteScalar().ToString();
}
}
I am populating a text box with the returned value of a function, but it doesn't work if I run the sql code inside the function. I can remove the sql related code and it works. so i'm stumped.
And by "doesn't work" i mean that the text box never gets populated with anything. it remains blank.
thanks
public string CreateResident()
{
string result = "hmm";
SqlConnection sqlConnection = new SqlConnection("Server=DELLXPS\\SQLEXPRESS; Initial Catalog=Warren_SEINDATASYSTEMS; Integrated Security=true;");
SqlCommand cmd = new SqlCommand();
cmd.CommandText = "INSERT INTO [dbo].[NewUsers]([ResidentAccountNumber],[ResidentName],[ResidentAddress],[NumberOfVisitors],[TempPass],[Role])VALUES(#ResidentAccountNumber,#ResidentName,#ResidentAddress,#NumberOfVisitors,(select cast((Abs(Checksum(NewId()))%10) as varchar(1)) + char(ascii('a')+(Abs(Checksum(NewId()))%25)) + char(ascii('A')+(Abs(Checksum(NewId()))%25)) + left(newid(),5)),'resident')";
cmd.CommandType = CommandType.Text;
cmd.Connection = sqlConnection;
SqlParameter ResidentAccountNumber = new SqlParameter();
ResidentAccountNumber.ParameterName = "#ResidentAccountNumber";
ResidentAccountNumber.Value = txtboxResidenetAccountNumber.Text.Trim();
cmd.Parameters.Add(ResidentAccountNumber);
SqlParameter ResidentName = new SqlParameter();
ResidentName.ParameterName = "#ResidentName";
ResidentName.Value = txtboxResidentName.Text.Trim();
cmd.Parameters.Add(ResidentName);
SqlParameter ResidentAddress = new SqlParameter();
ResidentAddress.ParameterName = "#ResidentAddress";
ResidentAddress.Value = txtboxResidentAddress.Text.Trim();
cmd.Parameters.Add(ResidentAddress);
SqlParameter NumberOfVisitors = new SqlParameter();
NumberOfVisitors.ParameterName = "#NumberofVisitors";
NumberOfVisitors.Value = txtboxNumberOfVisitors.Text.Trim();
cmd.Parameters.Add(NumberOfVisitors);
try
{
sqlConnection.Open();
result = (string)cmd.ExecuteScalar();
sqlConnection.Close();
}
catch (Exception ex)
{
result = ex.Message;
}
return result;
}
protected void btnCreateResident_Click(object sender, EventArgs e)
{
txtboxTempPassword.Text = CreateResident();
}
Your SQL is wrong and you have a lot of problems but I want to show you a way to make your code more readable. Format it like this:
cmd.CommandText = #"INSERT INTO [dbo].[NewUsers] ([ResidentAccountNumber],[ResidentName],[ResidentAddress], NumberOfVisitors],[TempPass], Role])
VALUES(
#ResidentAccountNumber,
#ResidentName,
#ResidentAddress,
#NumberOfVisitors,
(select cast((Abs(Checksum(NewId()))%10) as varchar(1)) + char(ascii('a')+(Abs(Checksum(NewId()))%25)) + char(ascii('A')+(Abs(Checksum(NewId()))%25)) + left(newid(),5)),
'resident')";
cmd.CommandType = CommandType.Text;
cmd.Connection = sqlConnection;
We know that a select in a VALUES constructor is not legal so that is one problem.
Also having a SELECT without a from seems strange -- did you copy your code correctly?
You are using ExecuteScalar -- do you know what that does? It shouldn't include a query that includes INSERT query.
I'm guessing you probably want a stored procedure.
I would suggest do not write query in C# code, you must use Stored Procedure for the same purpose.
If you want your query to return some id, primary key or some value then you must write query for that after your insert query.
you can use the following keywords in your select query,if you want to return id from table.
SCOPE_IDENTITY returns the last IDENTITY value inserted into an IDENTITY column in the same scope.
IDENT_CURRENT returns the last identity value generated for a specific table in any session and any scope.
##IDENTITY returns the last identity value generated for any table in the current session, across all scopes.
If you want to return only one record then use ExecuteScalar else you can use ExecuteReader.
If your only purpose is to insert data into the table then you should use ExecuteNonQuery.
With the help of comments I went with ExecuteReader instead of the ExecuteScaler. And changed the statement to return a value
INSERT INTO [table] ([fields]) OUTPUT Inserted.MyColumn VALUES(values)
C# Code:
reader = cmd.ExecuteReader();
try
{
while (reader.Read())
{
result = reader[0].ToString();
}
}
catch (Exception ex)
{
result = ex.Message;
}
return result;
I am trying to run the SQL Select query in my C# code. But I always get the -1 output on
int result = command.ExecuteNonQuery();
However, the same table if I use for delete or insert works...
ConnectString is also fine.
Please check below code
SqlConnection conn = new SqlConnection("Data Source=;Initial Catalog=;Persist Security Info=True;User ID=;Password=");
conn.Open();
SqlCommand command = new SqlCommand("Select id from [table1] where name=#zip", conn);
//command.Parameters.AddWithValue("#zip","india");
int result = command.ExecuteNonQuery();
// result gives the -1 output.. but on insert its 1
using (SqlDataReader reader = command.ExecuteReader())
{
// iterate your results here
Console.WriteLine(String.Format("{0}",reader["id"]));
}
conn.Close();
The query works fine on SQL Server, but I am not getting why only select query is not working.
All other queries are working.
SqlCommand.ExecuteNonQuery Method
You can use the ExecuteNonQuery to perform catalog operations (for example, querying the structure of a database or creating database objects such as tables), or to change the data in a database without using a DataSet by executing UPDATE, INSERT, or DELETE statements.
Although the ExecuteNonQuery returns no rows, any output parameters or return values mapped to parameters are populated with data.
For UPDATE, INSERT, and DELETE statements, the return value is the number of rows affected by the command. When a trigger exists on a table being inserted or updated, the return value includes the number of rows affected by both the insert or update operation and the number of rows affected by the trigger or triggers. For all other types of statements, the return value is -1. If a rollback occurs, the return value is also -1.
SqlCommand.ExecuteScalar Method
Executes a Transact-SQL statement against the connection and returns the number of rows affected.
So to get no. of statements returned by SELECT statement you have to use ExecuteScalar method.
Reference: http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.executenonquery(v=vs.110).aspx
So try below code:
SqlConnection conn = new SqlConnection("Data Source=;Initial Catalog=;Persist Security Info=True;User ID=;Password=");
conn.Open();
SqlCommand command = new SqlCommand("Select id from [table1] where name=#zip", conn);
command.Parameters.AddWithValue("#zip","india");
// int result = command.ExecuteNonQuery();
using (SqlDataReader reader = command.ExecuteReader())
{
if (reader.Read())
{
Console.WriteLine(String.Format("{0}",reader["id"]));
}
}
conn.Close();
According to MSDN
http://msdn.microsoft.com/ru-ru/library/system.data.sqlclient.sqlcommand.executenonquery(v=vs.110).aspx
result is the number of lines affected, and since your query is select no lines are affected (i.e. inserted, deleted or updated) anyhow.
If you want to return a single row of the query, use ExecuteScalar() instead of ExecuteNonQuery():
int result = (int) (command.ExecuteScalar());
However, if you expect many rows to be returned, ExecuteReader() is the only option:
using (SqlDataReader reader = command.ExecuteReader()) {
while (reader.Read()) {
int result = reader.GetInt32(0);
...
}
}
you can use ExecuteScalar() in place of ExecuteNonQuery() to get a single result
use it like this
Int32 result= (Int32) command.ExecuteScalar();
Console.WriteLine(String.Format("{0}", result));
It will execute the query, and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored.
As you want only one row in return, remove this use of SqlDataReader from your code
using (SqlDataReader reader = command.ExecuteReader())
{
// iterate your results here
Console.WriteLine(String.Format("{0}",reader["id"]));
}
because it will again execute your command and effect your page performance.
That is by design.
http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.executenonquery(v=vs.110).aspx
For UPDATE, INSERT, and DELETE statements, the return value is the number of rows affected by the command. When a trigger exists on a table being inserted or updated, the return value includes the number of rows affected by both the insert or update operation and the number of rows affected by the trigger or triggers. For all other types of statements, the return value is -1. If a rollback occurs, the return value is also -1.
you have to add parameter also #zip
SqlConnection conn = new SqlConnection("Data Source=;Initial Catalog=;Persist Security Info=True;User ID=;Password=");
conn.Open();
SqlCommand command = new SqlCommand("Select id from [table1] where name=#zip", conn);
//
// Add new SqlParameter to the command.
//
command.Parameters.AddWithValue("#zip","india");
int result = (Int32) (command.ExecuteScalar());
using (SqlDataReader reader = command.ExecuteReader())
{
// iterate your results here
Console.WriteLine(String.Format("{0}",reader["id"]));
}
conn.Close();
You should use ExecuteScalar() (which returns the first row first column) instead of ExecuteNonQuery() (which returns the no. of rows affected).
You should refer differences between executescalar and executenonquery for more details.
Hope it helps!
How to check if my table is empty from C#?
I have something like:
public MySqlConnection con;
public MySqlCommand cmd;
con = new MySqlConnection(GetConnectionString());
con.Open();
cmd = new MySqlCommand("SELECT * FROM data;", con);
Or I don't need to call SELECT statement?
You can use COUNT(*) with no WHERE close and see if exactly how many rows exist with the result.
Or you can do a SELECT (id) FROM tablename with no WHERE clause and if no rows are returned then the table is empty.
I'll give you an example in C# good luck
public bool checkEmptyTable(){
try
{
MySql.Data.MySqlClient.MySqlCommand com = new MySql.Data.MySqlClient.MySqlCommand();
conn = new MySql.Data.MySqlClient.MySqlConnection("YOUR CONNECTION");
com.Connection = conn;
com.CommandText = "SELECT COUNT(*) from data";
int result = int.Parse(com.ExecuteScalar().ToString());
return result == 0; // if result equals zero, then the table is empty
}
finally
{
conn.Close();
}
}
If 'data' might be a big table you would be better with this (where pkdata is your primary key field)
SELECT COUNT(*) FROM data WHERE pkdata = (SELECT pkdata FROM data LIMIT 1);
This will run very quickly whether you have 0 rows in 'data' or millions of rows. Using SELECT with no WHERE or ORDER BY means it just pulls the first row available, LIMIT 1 stops it getting more than 1.
Maybe something to look for if you have a program that ran very quickly six months ago but now runs like a dog in treacle!
SELECT COUNT(*)
FROM table
WHERE `col_name` IS NOT NULL