Develop Reference

SQL injection setString

Is there a possible way to inject some code in the the following statements (I tried the sleep function and it worked , but i'm looking for a way to get the table's name):
PreparedStatement statement = connection.prepareStatement(
"select password from " + USERS_TABLE_NAME + " where userid = ? and password = ?");
statement.setString(1, username_login);
statement.setString(2, password_login);

Using a prepared statement makes the code safe from SQL injection; the only way to inject some code into that query would be to tamper with USERS_TABLE_NAME somehow. I can't tell much about this as you didn't provide any code related to this, but if it's just a string constant you should be fine.

I read it can be be injectable using the ORDER BY clause !!
The example you showed above is not vulnerable to injection in the ORDER BY clause. The query doesn't even have an ORDER BY clause, or any string concatenation that could append an ORDER BY clause to the end of the query.
SQL injection can occur only if you allow untrusted content to modify the SQL query before passing it to the prepare() method.

Update command with special SQL keywords in JDBC

I am trying a update an entry in my SQL table which has a column name "from" in JDBC.
Following is the SQL command that I am trying to execute:
sql = "Update email_template set [from]="+"'"+3+"'"+" WHERE id="+idno;
stmt.executeUpdate(sql);
However it shows the following 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 '[from]='Akshit' WHERE id=1' at line

MySQL's way of escaping column names is by using backticks:
sql = "Update email_template set `from`="+"'"+3+"'"+" WHERE id="+idno;

I recommend using java.sql.PreparedStatement when handling SQL in Java. It can be used for batches and ensures malicious SQL is not injected as part of the SQL code.
This is how your code looks with a PreparedStatement:
PreparedStatement stmt = connection.prepareStatement("UPDATE `email_template` SET `from` = ? WHERE id = ?");
stmt.setInt(1, 3);
stmt.setInt(2, idno);
stmt.executeUpdate();
If this is an operation you execute for many rows in one go, replace stmt.executeUpdate() with stmt.addBatch() (likely in some loop) and when you're ready to execute the batched updates you call stmt.executeBatch().
Note that both executeUpdate() and executeBatch() return how many rows were affected; which is something you may want to validate after a commit.

Insert data to sql using java issue

I'm facing an issue with insertion to SQL database from java code.
I'm using INSERT sql query using the java code to enter the data from XML file to SQL database.
You may suppose column named "Description".
Imagine there is a record in XML which contains apostrophe ('). The program crashes due to the error caused by the apostrophe which is included in the data.
I know that manually we can add another apostrophe and make it work, but imagine data of 10.000 records, how can we handle this issue?

Don't do this (string concatenation):
String sql = "insert into MyTable (description) values ('" + value + "')";
Statement st = connection.createStatement();
st.executeUpdate(sql);
Do do this (prepared statement):
PreparedStatement ps = connection.prepareStatement(
"insert into MyTable (description) values (?)"
);
ps.setString(1, value);
pt.executeUpdate();
The value will get correctly escaped for you. Not only does this protect against mishaps like the one you mentioned, it also helps defend you from SQL injection attacks.
Humorous illustration:
Source

You have two options, you should use PreparedStatement and bind your parameter(s). Or, if you really, really, want - you could use StringEscapeUtils.escapeSql(str).

JDBC PreparedStatement with "?" in the column name

I am using a JDBC connection to fetch data from an Access database.
The database design is not my control. In the database there are columns that have "?" included in their names, for example: Open?, Paid?, and lots more.
When I try to fetch data with a PreparedStatement it gives me an error. The query is:
SELECT Open? FROM tblJobList WHERE WeekEnding=?
I also tried to use brackets like [Open?], but the result is the same.
The error I receive is "Too few parameters ..." as I am pushing only one parameter into the PreparedStatement.
I can not use normal statement because of WeekEnding=? as this value is a Timestamp and I could not manage to work it with Statement. Only prepared statement works here.
Can anyone tell me how to use these kind of column names in a PreparedStatement?

use the " character
"SELECT \"Open?\" FROM tblJobList WHERE WeekEnding=?"
tested this against oracle and appears to work with mssqlserver
How to select a column in SQL Server with a special character in the column name?

Just to update this for current technologies:
While the JDBC-ODBC Bridge and Access ODBC were unable to handle a PreparedStatement with a column name containing a question mark, the UCanAccess JDBC driver handles it just fine, as can be confirmed with the following code:
String connectionUrl = "jdbc:ucanaccess://C:/Users/Public/UCanAccessTest.accdb";
Connection conn = DriverManager.getConnection(connectionUrl);
String sql = "SELECT ID, [Open?] FROM tblJobList WHERE WeekEnding=?";
PreparedStatement ps = conn.prepareStatement(sql);
ps.setDate(1, java.sql.Date.valueOf("2016-01-01"));
ResultSet rs = ps.executeQuery();
while (rs.next()) {
System.out.printf("%d: %s%n", rs.getInt("ID"), rs.getBoolean("Open?"));
}
conn.close();
For more information on UCanAccess, see
Manipulating an Access database from Java without ODBC

I am not sure but you can try // to escape the special meaning of ? and to use it as a normal character. Like:
"SELECT Open//? FROM tblJobList WHERE WeekEnding=?"
You can get something similar to your problem here:
Round bracket in string with JDBC prepared statement

Escaping quotes in MSSQL is done by a double quote, so a '' or a "" will produce one escaped ' and ", respectively.

How to add records to databse via sql in Java

I am working a Airsoft application.
I'm trying to add records to a MS Access Database via SQL in Java. I have established a link to the database, with the following:
try
{
//String Driver = "sun.java.odbc.JdbcOdbcDriver";
Class.forName("net.ucanaccess.jdbc.UcanaccessDriver");
Connection conn = DriverManager.getConnection("jdbc:ucanaccess://" + URL,"","");
Statement stmt = conn.createStatement();
System.out.println("Connection Established!");
ResultSet rs = stmt.executeQuery("SELECT * FROM AirsoftGunRentals");
tblRent.setModel(DbUtils.resultSetToTableModel(rs));
}
catch(Exception ex)
{
JOptionPane.showMessageDialog(null, "Error");
}
I am using Ucanaccess to access my MS database. It is reading the database and is displaying to a JTable. However, I need to create three JButtons to add, delete and update the table. I have tried to code the add button, and I have tried to add a record, but it crashes and gives me errors.
try
{
//String Driver = "sun.java.odbc.JdbcOdbcDriver";
Class.forName("net.ucanaccess.jdbc.UcanaccessDriver");
Connection conn = DriverManager.getConnection("jdbc:ucanaccess://" + URL,"","");
Statement stmt = conn.createStatement();
System.out.println("Connection Established!");
String Query= "INSERT INTO AirsoftGunRentals(NameOfGun, Brand, TypeOfGuns, NumberOfMagazines,Extras,NumberAvailable,UnitRent)"+
"VALUES('"+pName+"','"+pBrand+"','"+pTypeOfGun+"','"+pNumMags+"','"+pExtras+"','"+pNumberAvail+"','"+pRent+"');";
ResultSet rs = stmt.executeQuery(Query);
JOptionPane.showMessageDialog(null, "Success!");
}
catch(Exception ex)
{
JOptionPane.showMessageDialog(null, "Error");
}
I have attempted all three, hoping for a result. But am still getting big errors. The only difference between the buttons is that one adds, one deletes and one updates the table. Other then that, the code is the same, minus variables.

As Brahim mentionned it, you should use stmt.executeUpdate(Query) whenever you update / insert or delete data. Also with this particular query, given your String concatenation (see end of line), there is no space between the ")" and the "VALUES" which probably causes a malformed query.
However, I can see from your code that you are not very experienced with such use-cases, and I'd like to add some pointers before all hell breaks loose in your project :
Use PreparedStatement instead of Statement and replace variables by placeholders to prevent SQL Injection.
The code that you are using here is extremely prone to SQL injection - if any user has any control over any of the variables, this could lead to a full database dump (theft), destruction of data (vandalism), or even in machine takeover if other conditions are met.
A good advice is to never use the Statement class, better be safe than sorry :)
Respect Java Conventions (or be coherent).
In your example you define the String Query, while all the other variables start with lower-case (as in Java Conventions), instead of String query. Overtime, such little mistakes (that won't break a build) will lead to bugs due to mistaking variables with classnames etc :)
Good luck on your road to mastering this wonderful language ! :)

First add a space before the quotation marks like this :
String Query= "INSERT INTO AirsoftGunRentals(NameOfGun, Brand, TypeOfGuns, NumberOfMagazines,Extras,NumberAvailable,UnitRent) "+
" VALUES('"+pName+"','"+pBrand+"','"+pTypeOfGun+"','"+pNumMags+"','"+pExtras+"','"+pNumberAvail+"','"+pRent+"');";
And use stmt.executeUpdate(Query); instead of : stmt.executeQuery(Query);in your insert, update and delete queries. For select queries you can keep it.

I managed to find an answer on how to add, delete and update records to a MS Access DB. This is what I found, after I declared the connection, and the prepped statement. I will try to explain to the best I can. I had to add values individually using this:
(pstmt = Prepped Statement Variable)
pstmt.setWhatever(1,Variable);
And it works fine now. I use the same method to delete and update records.
This is the basic query format:
String SQLInsert = "INSERT INTO Tbl VALUES(NULL,?,?,?,?)";
The NULL in the statement is the autonumber in the table. and .setWhatever() clause replaces the question marks with the data types. Thus manipulating the database.
Thank you everyone for all your contributions. It helped a lot, and made this section a lot more understandable.