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System.Data.SqlClient.SqlException: 'Incorrect syntax near the keyword 'where'.' ||||who can help me with this error?

the code is below and the error starting from sqlCommand cmd the 13th line of this code
private void button2_Click(object sender, EventArgs e)
{
if (StudenUsn.Text == "" )
{
MessageBox.Show("Enter The Student Number");
} else {
Con.Open();
String query = "update Student_tbl set StdName='" + StudName.Text + "',where FatherName='" + FtName.Text + "',where MotherName='" + MtName.Text + "',where StdAddress='" + Address.Text + "',where Collage ='" + Collage.Text + "'set StdRoom = " + StRmNum.SelectedValue.ToString()+",StdStatus = '"+ StudSt.SelectedItem.ToString() + "' where StdUsn ='"+StudenUsn+ "')";
SqlCommand cmd = new SqlCommand(query, Con);
cmd.ExecuteNonQuery();
MessageBox.Show("Room Successfully Updates");
Con.Close();
FillStudentDGV();
}
}

Your code should look more like:
private void button2_Click(object sender, EventArgs e)
{
if (StudenUsn.Text == "" )
{
MessageBox.Show("Enter The Student Number");
} else {
var query = #"
update Student_tbl
set
StdName=#sn,
FatherName=#fn,
MotherName=#mn,
StdAddress=#sa,
Collage=#c,
StdRoom=#sr,
StdStatus=#ss
where
StdUsn=#su";
using var con = new SqlConnection(YOUR_CONN_STR_HERE);
using var cmd = new SqlCommand(query, con);
cmd.Parameters.AddWithValue(#sn, StudName.Text);
cmd.Parameters.AddWithValue(#fn, FtName.Text);
cmd.Parameters.AddWithValue(#mn, MtName.Text);
cmd.Parameters.AddWithValue(#sa, Address.Text);
cmd.Parameters.AddWithValue(#c, Collage.Text);
cmd.Parameters.AddWithValue(#sr, StRmNum.SelectedValue);
cmd.Parameters.AddWithValue(#ss, StudSt.SelectedItem);
cmd.Parameters.AddWithValue(#su, StudenUsn);
con.Open();
cmd.ExecuteNonQuery();
con.Close();
MessageBox.Show("Room Successfully Updates");
FillStudentDGV();
}
}
There are good reasons to avoid using AddWithValue if you use SQLServer which you can get into at a later date if you want, but it's convenient for me (who doesn't know the types and widths of your columns) dealing with the current massive elephant in the room which is your SQL is massively vulnerable to a hacking technique known as sql injection (and to a lesser extent it would blow up with an error for any student whose name included an apostrophe) - using AddWithValue might make your query slightly slower, but better that than it be the cause of the next data breach; learn how to write SQLs right, right now
Never ever take data supplied by a user and concatenate it into an SQL string. Doing so essentially, in most cases, gives the user access to your database. So many big companies whose developers should know better, put up expensive firewalls and security and then let anyone in via this back door anyway; sql injection prone systems are one of the leading causes of hacks in the world today
Always use #parameter placeholders in the SQL for user data and add a parameter to the command's parameters collection, containing the data
Now on the topic of your actual error; the pattern for an update is
update table
set col1=#param1, col2=#param2 ...
where (some conditions)
You have one where and one set. If there is some conditional aspect to your set, like you only want to update the student name/address if it is currently null then you can do like:
update table
set
name=case when name is null then #n else name end,
address=case when address is null then #a else address end
where (some conditions)
Or more simply
update table
set
name=coalesce(name, #n)
address=coalesce(address, #a)
where (some conditions)
You can't mix n match and say "where this=that where this2=that2 set this3=that3" - that's a syntax error. Where is for picking the row you want to update and set is for starting a block of commas separated columns and values the row data is to be updated to.
Strive to write your sql nicely formatted inside an #string; it's a programming language all of its own, and will be easier to debug if it's laid out nicely

Can u try with it ?
String query = "update Student_tbl set StdName='" + StudName.Text + "',StdRoom = '" + StRmNum.SelectedValue.ToString()+"',StdStatus = '"+ StudSt.SelectedItem.ToString() + "' where FatherName='" + FtName.Text + "' and MotherName='" + MtName.Text + "' and StdAddress='" + Address.Text + "' and Collage ='" + Collage.Text + "' and StdUsn ='"+StudenUsn+ "'";

Setting SQL query parameter to Int32 in C#

I'm having problems with some code I'm trying to write. I'm doing something for suppliers orders, so I have a table which is named "encomendas_fornecedores" with a autoincrement field before the key that is the code of sale which consists in a EF before the number(which is a text field).
Here is the code:
connection.Open();
OleDbCommand comando1 = new OleDbCommand();
OleDbCommand comando2 = new OleDbCommand();
OleDbCommand comando3 = new OleDbCommand();
comando1.Connection = connection;
comando2.Connection = connection;
comando3.Connection = connection;
comando1.CommandText = "INSERT INTO encomendas_fornecedores (cod_encomenda_forn, cod_metodo, cod_forn, total_pagar_forn) VALUES('FO', '" + txtcodmetodo.Text + "', '" + txtcodforn.Text + "', '" + lbltotalapagar.Text + "'); ";// insert into table the values with a FO to cod
comando1.ExecuteNonQuery();
comando2.CommandText = "Select MAX(num_encomenda) From encomendas_fornecedores;";// selecting maximum num encomenda so I can isolate it and add to a text before(btw I do this in php/sql no problems
int numero = Convert.ToInt32(comando2.ExecuteScalar());//max num_encomenda
string codencomendaforn= "EF"+Convert.ToString(numero);// sales code completed
comando3.CommandText = "UPDATE encomendas_fornecedores SET cod_encomenda_forn = '"+codencomendaforn+"' WHERE num_encomenda = '"+ numero +"';";//query that is giving me the problems, it says something like "type of data incorrect in data expression"
comando3.ExecuteScalar();//giving me error this line
connection.Close();
But now here's the catch the cod_encomenda_forn is text and the num_encomenda auto increment as it is in the sql, and I tried to show the query in a textbox to see if its anything is wrong but nothing seems wrong.

"UPDATE encomendas_fornecedores SET cod_encomenda_forn = '"+codencomendaforn+"' WHERE num_encomenda = **'**"+ **numero** +"**'**;";//query that is giving me the problems,it says something like "type of data incorrect in data expression"
You are passing a string numero to a where statement that seems like it is expecting a number. As long as it is numeric it should work, but definitely not gauranteed to work. Second you are passing anothercodencomendaforn string to encomenda what is encomenda 's data type?
It appears that you are not handling potential datatype differences between your c# code and your SQL query. In addition single quoting '' around a value in a SQL statement tells the database engines that it is a string even if that is '1234'. While SQL will automatically convert some values it doesn't always. In addition c# .net library also looks for some conversion etc. before sending the SQL statement. To fix appropriately use parameters that are data typed to the database type in the SQL table. To fix it simply in the statement figure out your data types and fix the '' single quotes appropriately.
PS the people trying to help you in the comments were being nice and telling you the professional way of keeping your job in the future when you graduate after fixing this issue.

Insert into DateTime (from C# to MySQL)

I Just Keep Having this Error:
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 '2014-10-08 19:39:57)' at line 1
public string ObtenerFechaHora()
{
string query = "select CURRENT_TIMESTAMP() as Fecha";
OpenConnection();
MySqlCommand cmd = new MySqlCommand(query, connection);
cmd.ExecuteNonQuery();
DateTime e = (DateTime)cmd.ExecuteScalar();
CloseConnection();
return e.ToString("yyyy-MM-dd H:mm:ss");
}
Then i insert ("Fecha" is the DateTime Column)
string query = "INSERT INTO actividad (idTerminal, Proceso, Nombre, Tiempo, Fecha) VALUES('" + idTerminal + "', '" + Proceso + "', '" + Nombre + "', '1,'" + this.ObtenerFechaHora() + ")";
I been used loot of formats and i keep having error, for example:
e.ToString("yyyy-MM-dd H:mm:ss");
e.ToString("yyyy-MM-dd HH:mm:ss");
e.ToString("dd-MM-yyyy H:mm:ss");
e.ToString("yyyy-dd-MMH:mm:ss");
Also with "/" instead of "-"
Any help here?

The problem isn't with the format of the datetime string; the problem is in the SQL text of the INSERT statement, right before the value is appended. For debugging this, you could output the query string and inspect it.
The problem is in the SQL text here:
+ "', '1,'" +
There needs to be a comma between that literal and the next column value. It looks like you just missed a single quote:
+ "', '1','" +
^
A potentially bigger problem is that your code appears to be vulnerable to SQL Injection. Consider what happens when one of the variables you are including into the SQL text includes a single quote, or something even more nefarios ala Little Bobby Tables. http://xkcd.com/327/.
If you want a column value to be the current date and time, you don't need to run a separate query to fetch the value. You could simply reference the function NOW() in your query text. e.g.
+ "', '1', NOW() )";

You excuted twice
//cmd.ExecuteNonQuery();
DateTime e = (DateTime)cmd.ExecuteScalar();
Should be only one time.
Then like #sgeddes said in the comments use parameterized queries, they avoid errors and sql injections.

The approach that you have used is not the best approach to write SQL command. You should use sql parameters in the Query. Your code is vulnerable to SQL Injected and obviously it is not the best approach.
Try using something like this:
string commandText = "UPDATE Sales.Store SET Demographics = #demographics "
+ "WHERE CustomerID = #ID;";
SqlCommand command = new SqlCommand(commandText, connection);
command.Parameters.Add("#ID", SqlDbType.Int);
command.Parameters["#ID"].Value = customerID;

Getting SQLException when debugging

I've got a error which I can't understand. When I'm debugging and trying to run a insert statement, its throwing the following exception:
"There are fewer columns in the INSERT statement than values specified in the VALUES clause. The number of values in the VALUES clause must match the number of columns specified in the INSERT statement."
I have looked all over my code, and I can't find the mistake I've made.
This is the query and the surrounding code:
SqlConnection myCon = DBcon.getInstance().conn();
int id = gm.GetID("SELECT ListID from Indkøbsliste");
id++;
Console.WriteLine("LNr: " + listnr);
string streg = GetStregkode(navne);
Console.WriteLine("stregk :" + strege);
string navn = GetVareNavn(strege);
Console.WriteLine("navn :" + navne);
myCon.Open();
string query = "INSERT INTO Indkøbsliste (ListID, ListeNr, Stregkode, Navn, Antal, Pris) Values(" + id + "," + listnr + ", '" + strege + "','" + navn + "'," + il.Antal + ", "+il.Pris+")";
Console.WriteLine(il.Antal+" Antal");
Console.WriteLine(il.Pris+" Pris");
Console.WriteLine(id + " ID");
SqlCommand com = new SqlCommand(query, myCon);
com.ExecuteNonQuery();
com.Dispose();
myCon.Close();

First of all check the connection string and confirm the database location and number of columns a table has.
Suggestion : Do not use hardcoded SQL string. Use parameterized sql statements or stored-proc.
Try parameterized way,
string query = "INSERT INTO Indkøbsliste (ListID, ListeNr, Stregkode, Navn, Antal, Pris)
Values (#ListID, #ListeNr, #Stregkode, #Navn, #Antal, #Pris)"
SqlCommand com = new SqlCommand(query, myCon);
com.Parameters.Add("#ListID",System.Data.SqlDbType.Int).Value=id;
com.Parameters.Add("#ListeNr",System.Data.SqlDbType.Int).Value=listnr;
com.Parameters.Add("#Stregkode",System.Data.SqlDbType.VarChar).Value=strege ;
com.Parameters.Add("#Navn",System.Data.SqlDbType.VarChar).Value=navn ;
com.Parameters.Add("#Antal",System.Data.SqlDbType.Int).Value=il.Antal;
com.Parameters.Add("#Pris",System.Data.SqlDbType.Int).Value=il.Pris;
com.ExecuteNonQuery();

Please always use parametrized queries. This helps with errors like the one you have, and far more important protects against SQL injection (google the term, or check this blog entry - as an example).
For example, what are the actual values of strege and/or navn. Depending on that it may render your SQL statement syntactically invalid or do something worse.
It (looks like) a little more work in the beginning, but will pay off big time in the end.

Are you using danish culture settings?
In that case if il.Pris is a double or decimal it will be printed using comma, which means that your sql will have an extra comma.
Ie:
INSERT INTO Indkøbsliste (ListID, ListeNr, Stregkode, Navn, Antal, Pris) Values(33,5566, 'stegkode','somename',4, 99,44)
where 99,44 is the price.
The solution is to use parameters instead of using the values directly in you sql. See some of the other answers already explaining this.

How to solve a syntax error when using this INSERT INTO statement and the .NET OleDb namespace?

I keep getting an error when I attempt to insert values into a Access database.
The error is syntactic, which leads to the following exception:
OleDbException was unhandled Syntax error in INSERT INTO statement.
private OleDbConnection myCon;
public Form1()
{
InitializeComponent();
myCon = new OleDbConnection(#"Provider=Microsoft.Jet.OLEDB.4.0; Data Source=C:\File.mdb");
}
private void insertuser_Click(object sender, EventArgs e)
{
OleDbCommand cmd = new OleDbCommand();
myCon.Open();
cmd.Connection = myCon;
cmd.CommandType = CommandType.Text;
cmd.CommandText = "INSERT INTO User ([UserID], [Forename], [Surname], " +
"[DateOfBirth], [TargetWeight], [TargetCalories], [Height]) " +
"VALUES ('" + userid.Text.ToString() + "' , '" +
fname.Text.ToString() + "' , '" +
sname.Text.ToString() + "' , '" +
dob.Text.ToString() + "' , '" +
tarweight.Text.ToString() + "' , '" +
tarcal.Text.ToString() + "' , '" +
height.Text.ToString() + "')";
cmd.ExecuteNonQuery();
myCon.Close();
}

Well, you haven't specified what the error is - but your first problem is that you're inserting the data directly into the SQL statement. Don't do that. You're inviting SQL injection attacks.
Use a parameterized SQL statement instead. Once you've done that, if you still have problems, edit this question with the new code and say what the error is. The new code is likely to be clearer already, as there won't be a huge concatenation involved, easily hiding something like a mismatched bracket.
EDIT: As mentioned in comments, Jet/ACE is vulnerable to fewer types of SQL injection attack, as it doesn't permit DML. For this INSERT statement there may actually be no vulnerability - but for a SELECT with a WHERE clause written in a similar way, user input could circumvent some of the protections of the WHERE clause. I would strongly advise you to use parameterized queries as a matter of course:
They mean you don't have to escape user data
They keep the data separate from the code
You'll have less to worry about if you ever move from Jet/ACE (whether moving this particular code, or just you personally starting to work on different databases)
For other data types such as dates, you don't need to do any work to get the data into a form appropriate for the database
(You also don't need all the calls to ToString. Not only would I expect that a property called Text is already a string, but the fact that you're using string concatenation means that string conversions will happen automatically anyway.)

I posted this as a comment to the duplicate question at: Syntax error in INSERT INTO statement in c# OleDb Exception cant spot the error
Put brackets [] around the table name
"User". It's a reserved word in SQL
Server.
"User" is also a reserved word in Access (judging by the provider in your connection string).
But I completely agree with Jon--if you fix your current implementation, you are just opening up a big security hole (against your User table, no less!)

This problem may occur if your database table contains column names that use Microsoft Jet 4.0 reserved words.
Change the column names in your database table so that you do not use Jet 4.0 reserved words.

If TargetWeight, Height, and TargetCalories are floating-point or integer values, they don't need to be surrounded by quotes in the SQL statement.
Also, not directly related to your question, but you should really consider using a parameterized query. Your code is very vulnerable to SQL injection.

public decimal codes(string subs)
{
decimal a = 0;
con_4code();
query = "select SUBJINTN.[SCODE] from SUBJINTN where SUBJINTN.[ABBR] = '" + subs.ToString() + "'";
cmd1 = new OleDbCommand(query, concode);
OleDbDataReader dr = cmd1.ExecuteReader();
here is error in dr it says syntax error ehile in DBMS its working Well
if (dr.Read())
{
a = dr.GetDecimal(0);
MessageBox.Show(a.ToString());
}
return a;
}

After this
cmd.CommandText="INSERT INTO User ([UserID], [Forename], [Surname], [DateOfBirth], [TargetWeight], [TargetCalories], [Height]) Values ('" + userid.Text.ToString() + "' , '" + fname.Text.ToString() + "' , '" + sname.Text.ToString() + "' , '" + dob.Text.ToString() + "' , '" + tarweight.Text.ToString() + "' , '" + tarcal.Text.ToString() + "' , '" + height.Text.ToString() + "')";
check what this contains, maybe [DateOfBirth] has illegal format