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SQL query for updating column with values from a local variable

How can I update my SQL Table column with the value that is stored in a local variable.
In my program I have taken value from the HTML page using the following statement:
String idd=request.getParameter("id");
String report=request.getParameter("rprt");
So now I have to update the value of report in my database table named "ptest" and I am using the following query:
Class.forName("com.mysql.jdbc.Driver");
java.sql.Connection con =
DriverManager.getConnection("jdbc:mysql://localhost:3306/tcs","root","root");
Statement st= con.createStatement();
ResultSet rs;
int i=st.executeUpdate("update ptest set result = #reprt where patient_id=
#idd");
out.println("Successfully Entered");
But the value is not being stored in the database instead NULL is being stored.
I have already seen this question and got no help.
Question
Please ignore my mistakes if any in this question as I am new to MYSQL.

You can use prepared statements in java.
setString or setInt can set different data types into your prepared statements.
The parameter 1, 2 are basically the positions of the question mark. setString(1,report) means that it would set the string report in the 1st question mark in your query.
Hope this code helps you in achieving what you want.
String query = "update ptest set result = ? where patient_id = ?";
PreparedStatement preparedStatement = con.prepareStatement(query);
preparedStatement.setString(1, report);
preparedStatement.setString(2, idd);
preparedStatement.executeUpdate();

In JDBC, you use ? as placeholders for where you want to inject values into a statement.
So you should do something like this ...
Class.forName("com.mysql.jdbc.Driver");
java.sql.Connection con =
DriverManager.getConnection("jdbc:mysql://localhost:3306/tcs","root","root");
PreparedStatement st= con.prepareCall("update ptest set result = ? where patient_id=
?");
///now set the params in order
st.setString(1, report);
st.setString(2, idd);
//then execute
st.executeUpdate();
Doing a string concat with the values is dangerous due to sql injection possibilities, so I typically make statement text static and final, and also if your value has a ' in it that could blow up your sql syntax etc. Also, notice the use of executeUpdate rather than query.
Hope this helps

Why does this Query return NULL?

I have a derby users database which I query, when the user clicks login on the application.
However, when I query the users table with the parameter [user] derby returns a null Object instead of the record it ought to return.
Here is my code:
String ssql = "SELECT * FROM USERS WHERE UNAME LIKE ?";
try{
DriverManager.registerDriver(new org.apache.derby.jdbc.EmbeddedDriver());
con = DriverManager.getConnection(url);
sql = con.prepareStatement(ssql, Statement.RETURN_GENERATED_KEYS);
sql.setString(1, cbox_chooseUser.getSelectedItem().toString());
sql.executeQuery();
ResultSet rs = sql.getGeneratedKeys();
try{
while (rs.next()) {
if(rs.getString("PW").toCharArray().equals(txt_password.getPassword())){
sql.close();
con.close();
return true;
}
} catch (NPE ...) {...}
}
I tried it multiple times wit a test user with both the pw and the username set to "test"; but I always get the same error.
Why is the recordset always Null?
Thanks for your help :)

The documentation says
ResultSet getGeneratedKeys() throws SQLException
Retrieves any auto-generated keys created as a result of executing this Statement
object.
If this Statement object did not generate any keys, an empty
ResultSet object is returned.
Your select statement isn't generating any keys that's why it's returning an empty ResultSet. You aren't inserting anything hence no keys are being generated.
You can try ResultSet rs = sql.executeQuery();. It should work.

You are using it in wrong way.
The generated keys concept should be used only in the case DML of insert type query but not in the case of select query.
select simply select the rows from the table. In this case there is no chance of any keys getting generated.
In the case of insert query if any column is configured as auto increment or kind of functionality then some keys will get generated. These keys can be caught using Statement.RETURN_GENERATED_KEYS in java.
As you are using select query there is no need of using Statement.RETURN_GENERATED_KEYS.
You just modify below lines and everything will be fine.
sql = con.prepareStatement(ssql, Statement.RETURN_GENERATED_KEYS);
sql.setString(1, cbox_chooseUser.getSelectedItem().toString());
sql.executeQuery();
ResultSet rs = sql.getGeneratedKeys();
with
sql = con.prepareStatement( ssql );
sql.setString( 1, cbox_chooseUser.getSelectedItem().toString() );
ResultSet rs = sql.executeQuery();

Can have two database connection in one function?

When I debug, I get this error :
Column 'place1' not found.
I was able to verify that it has column place1 in sql.
Is it because I can not have two database connection in one function? I am unsure on how to further debug the problem.
Case.java
System.out.println("The highest value is "+highest+"");
System.out.println("It is found at index "+highestIndex+""); // until now it works fine
String sql ="Select Day from menu where ID =?";
DatabaseConnection db = new DatabaseConnection();
Connection conn =db.getConnection();
PreparedStatement ps = conn.prepareStatement(sql);
ps.setInt(1, highestIndex);
ResultSet rs = ps.executeQuery();
if (rs.next())
{
int kb=rs.getInt("Day");
System.out.println(kb);
if(kb==k) // k is a value getting from comboBox
{
String sql1 ="Select * from placeseen where ID =?";
DatabaseConnection db1 = new DatabaseConnection();
Connection conn1 =db1.getConnection();
PreparedStatement ps1 = conn.prepareStatement(sql);
ps.setInt(1, highestIndex);
ResultSet rs1 = ps.executeQuery();
if (rs1.next())
{
String aaa=rs1.getString("place1");
String bbb=rs1.getString("place2");
Tourism to =new Tourism();
to.setPlace1(aaa);
to.setPlace2(bbb);
DispDay dc=new DispDay();
}
ps1.close();
rs1.close();
conn1.close();
}
else
{
System.out.print("N");
System.out.println("Sorry!!!");
}
}
ps.close();
rs.close();
conn.close();

Trace your code to see where you're getting the data. The error is on this line:
String aaa=rs1.getString("place1");
Where does rs1 come from?:
ResultSet rs1 = ps.executeQuery();
Where does ps come from?:
PreparedStatement ps = conn.prepareStatement(sql);
Where does sql come from?:
String sql ="Select Day from menu where ID =?";
There's no column being selected called place1. This query is only selecting a single column called Day.
Maybe you meant to get the result from the second prepared statement?:
ResultSet rs1 = ps1.executeQuery();
There are probably more such errors. Perhaps several (or many) more. Because...
Hint: Using meaningful variable names will make your code a lot easier to follow. ps, ps1, rs1, etc. are very easy to confuse. Name variables by the things they conceptually represent and your code starts to read like a story which can be followed. Variable names like daysQuery and daysResults and placesResults make it more obvious that something is wrong when you try to find a "place" in a variable which represents "days".

In your second query:
PreparedStatement ps1 = conn.prepareStatement(sql);
you are accidentally using the variable sql instead of your previously defined sql1. Replace it and it will be ok.

PreparedStatement throws syntax error [duplicate]

This question already has answers here:
MySQLSyntaxErrorException near "?" when trying to execute PreparedStatement
(2 answers)
Closed 7 years ago.
Im preparing a query using PreparedStatements and it runs fine when i hardcode te query with the condition parameter.
but throws error , if the parameter is passed from setString() method.
com.mysql.jdbc.JDBC4PreparedStatement#2cf63e26: select * from linkedin_page_mess ages where company_id = '2414183' com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: 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 '?' at line 1
In the error log, above my query looks fine.
public JSONObject getLinkedInMessages(String compId)
{
linlogger.log(Level.INFO, "Called getLinkedInMessages method");
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
JSONObject resObj = new JSONObject();
JSONArray tempArray = new JSONArray();
try
{
conn = InitOrGetConnection();
String query = "select * from linkedin_page_messages where company_id = ?";
PreparedStatement pst=conn.prepareStatement(query);
pst.setString(1, compId);
System.out.println("\n\n"+pst.toString());
rs= pst.executeQuery(query);
// process resultset logics
}
catch(Exception e)
{
System.out.println(e);
linlogger.log(Level.INFO, "Exception occured "+e.toString());
}
}
Is there anything wrong with the PreparedStatements?

Remove the parameter from
rs= pst.executeQuery(query);
change to
rs= pst.executeQuery();
If you pass query in pst.executeQuery(query); as parameter then this passed query string take priority over the query string you passed in conn.prepareStatement(query); and since in query(select * from linkedin_page_messages where company_id = ?) you dint pass parameter you get the error.

remove the parameter in this line:
rs= pst.executeQuery(query);
It must be
rs= pst.executeQuery();
Because the statement is prepared at PreparedStatement pst=conn.prepareStatement(query);
execute(String sql) is inherited from Statement and will execute the satement (sql) without prepared it.

need to retrieve a database row value via sql based on values retrieved via previous sql query in java

My code goes something like this
DataBaseUtil dbBaseUtil=new DataBaseUtil();
Connection con=dbBaseUtil.getConnection();
String query="select case_id, ticket_id from VAPP_ITEM where
(person1_alt_email='" + username +"') and ticket_type='Service Request' and ticket_status not in ('Closed','Resolved')";
ResultSet rs=dbBaseUtil.getDbResultSet(query);
List<String> tickets=new ArrayList<String>();
while(rs.next())
ticket.add(rs.getString("case_Id")+"-"+rs.getString("ticket_Id"));
MyTicketUtil.searchAndOpenTicket(webui, "", tickets.get(0));
Now, once I get the element "tickets(0)", I perform some operations on it, and after the operations are performed, I need to retrieve ticket_status for the ticket on which the operations were performed - tickets(0).
However, to query the database, I need case_id and ticket_id for tickets(0). How can it be done?
I tried creating two ResultSets and a query post operations like below:
while(rs1.next())
quer1 = "select ticket_status from VAPP_ITEM where case_id=rs.getString(1) and ticket_id = rs.getString(2)";
But this is not working - console shows below error:
com.microsoft.sqlserver.jdbc.SQLServerException: Cannot find either column "rs" or the user-defined function or aggregate "rs.getString", or the name is ambiguous.

You have included rs.getString() into string literal.
You should use PreparedStatement for such things:
quer1 = "SELECT ticket_status FROM vapp_item WHERE case_id=? AND ticket_id = ?";
PreparedStatement pstm = conn.prepareStatement(quer1);
while (rs1.next())
{
pstm.setString(1, rs.getString(1));
pstm.setString(2, rs.getString(2));
rs2 = pstm.executeQuery();
...
}