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How can I only get 1 element from a SQL Database?

I have a small problem. I wrote a method in which I have an SQL query that should output a correct string after 2 parameters. When debugging, however, the result is not the right element. I don't know why this happens.
public static String findRightTemplate(String user_name, int template_id)
throws Exception {
Connection conn = DriverManager.getConnection(
"xxx", "xxx", "xxx");
Statement st = conn.createStatement();
st = conn.createStatement();
ResultSet rs = st.executeQuery(
"SELECT template FROM templates " +
"where template_id=template_id AND user_name=user_name"
);
String temp="";
while(rs.next())
{
temp=rs.getString("template");
}
rs.close();
st.close();
conn.close();
I ask for the username and template_id and I just want to get an element out of the template column.
The SQL query is correct. I've already tested that. But it seems that the query runs through all elements with the same username. As a result, I only get the last element and not the right one.
UPDATE

Currently you do not use the method parameters inside your query. As already suggested you should use a PreparedStatement to fix that. You should basically do the following:
public static String findRightTemplate(String userName, int templateId) throws SQLException {
try (final Connection connection = DriverManager.getConnection("...")) {
final PreparedStatement preparedStatement = connection.prepareStatement(
"SELECT template " +
"FROM templates " +
"WHERE user_name = ? " +
"AND template_id = ? " +
"LIMIT 1"
);
preparedStatement.setString(1, userName);
preparedStatement.setInt(2, templateId);
final ResultSet resultSet = preparedStatement.executeQuery();
if (resultSet.next()) {
return resultSet.getString(1);
}
}
return null;
}
If you do not use a PreparedStatement and build the query manually as suggested in the comments your application could be vulnerable to SQL injection attacks.

Java - Sql query with Alias

I want to retrieve a particular column from the database. For a simple Select statement, I can able to able to retrieve a column like below
public String getDbColumnValue(String tableName, String columnName, String applicationNumber) {
String columnValue = null;
try {
PreparedStatement ps = null;
String query = "SELECT " + columnName + " FROM " + tableName +
" WHERE ApplicationNumber = ?;";
ps = conn.prepareStatement(query);
ps.setString(1, applicationNumber);
ResultSet rs = ps.executeQuery();
if (rs.next()) {
columnValue = rs.getString(columnName);
return columnValue;
}
}
catch (Exception ex) {
}
return columnValue;
}
But, I'm using alias in my query like below. And this query works fine. How to use this in Java to retrieve a particular column
select S.StatusDesc from application A, StatusMaster S
where A.StatusMasterId = S.StatusMasterId and A.ApplicationNumber = '100041702404'
Any help would be greatly appreciated!

I think you are confusing simple aliases, which are used for table names, with the aliases used for column names. To solve your problem, you can just alias each column you want to select with a unique name, i.e. use this query:
select S.StatusDesc as sc
from application A
inner join StatusMaster S
on A.StatusMasterId = S.StatusMasterId and
A.ApplicationNumber = '100041702404'
Then use the following code and look for your aliased column sc in the result set.
PreparedStatement ps = null;
String query = "select S.StatusDesc as sc ";
query += "from application A ";
query += "inner join StatusMaster S ";
query += "on A.StatusMasterId = S.StatusMasterId ";
query += "and A.ApplicationNumber = ?";
ps = conn.prepareStatement(query);
ps.setString(1, applicationNumber);
ResultSet rs = ps.executeQuery();
if (rs.next()) {
columnValue = rs.getString("sc");
return columnValue;
}
Note: I refactored your query to use an explicit inner join instead of joining using the where clause. This is usually considered the better way to write a query.

Java- select certain rows from column with SQLite

Sorry if the title is not precise.
I am using a custom class to get data from a SQLite database.
For example:
the method below is supposed to return list of users, which are members of a certain department.
Each user in the USER table has a column with id of the department he belongs to.
At the moment I am getting all the users and then comparing their department IDs to the targetID of the department I am looking for.
Is there a way to get just the set of users that have a particular department ID, so that I don't have to check each one's department id?
private List<User> getDepartmentMembers(int targetID) {
List<User> members = new ArrayList<User>();
Connection c = null;
Statement statement = null;
try {
Class.forName("org.sqlite.JDBC");
c = DriverManager.getConnection("jdbc:sqlite:TheatroData.sqlite");
c.setAutoCommit(false);
statement = c.createStatement();
ResultSet rs = statement.executeQuery( "SELECT * FROM USERS;" );
while ( rs.next() ) {
int id = rs.getInt(Constants.ID_KEY);
if (id == targetID ){
User tmp = null;
int position = rs.getInt(Constants.POSITION_KEY);
if (position == Constants.DEPARTMENT_HEAD)
tmp = new DepartmentHead();
else if (position == Constants.DEPARTMENT_MANAGER)
tmp = new DepartmentManager();
else if (position == Constants.DEPARTMENT_MEMBER);
tmp = new GruntUser();
tmp.setID(id);
tmp.setName(rs.getString(Constants.NAME_KEY));
tmp.setPosition(position);
tmp.setUsername(rs.getString(Constants.USERNAME_KEY));
tmp.setLastname(rs.getString(Constants.SURNAME_KEY));
tmp.setDepartment(targetID);
tmp.setPassword(rs.getString(Constants.PASS_KEY));
members.add(tmp);
}
}
rs.close();
statement.close();
c.close();
} catch ( Exception e ) {
System.err.println( e + " -in getDepartmentMembers" + e.getClass().getName() + ": " + e.getMessage());
}
return members;
}
I was thinking I need something like this:
ResultSet rs = statement.executeQuery( "SELECT * FROM USERS where department = ?;", targetID );

In an ideal world, you could do it as you wrote:
ResultSet rs = statement.executeQuery( "SELECT * FROM USERS WHERE department = ?;", targetID );
But, executeQuery from JDBC does currently not provide the possibility for argument binding. So you have to use "Prepared Statements".
Instead of
statement = c.createStatement();
ResultSet rs = statement.executeQuery( "SELECT * FROM USERS;" );
do:
prepared = c.prepareStatement("SELECT * FROM USERS WHERE department = ?;");
prepared.setString(1, targetID);
ResultSet rs = prepared.executeQuery();
When you need more than one parameter, you can use a different syntax for replacing it, for example "?001". See SQLite Documentation: C/C++ Interface Section 5.
Also remove the Java coding for your own selection of the right department.
Since the CluelessStudent presented a different solution, involving string concatenation, I want to say the following:
I would definitively discourage string concatenation! You always
should use argument binding and not string concatenation! String
concatenation is a huge security risk, since it can be used for so
called "SQL injection attacks". See Wikipedia: SQL Injection

Yes you pratcially answered your own question. You can also do like this.
String query = "SELECT * FROM USERS where department = (?)";
PreparedStatement statement = c.prepareStatement(sql);
statement.setInt(1, targetId);
ResultSet rs = statement.executeQuery();
while(rs.next()){
//you get only records that have id = targetId
}
//close rs, statement and connection!!!

I was just passing a wrong statement. The correct way:
ResultSet rs = statement.executeQuery( "SELECT * FROM USERS where department = "+targetID+";");

setString for prepared statement not working

I am trying to use the setString(index, parameter) method for Prepared Statements in order to create a ResultSet but it doesn't seem to be inserting properly. I know the query is correct because I use the same one (minus the need for the setString) in a later else. Here is the code I currently have:
**From what I understand, the ps.setString(1, "'%" + committeeCode + "%'"); is supposed to replace the ? in the query but my output says otherwise. Any help is appreciated.
public String getUpcomingEvents(String committeeCode) throws SQLException{
Context ctx = null;
DataSource ds = null;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
StringBuilder htmlBuilder = new StringBuilder();
String html = "";
try {
ctx = new InitialContext();
ds = (DataSource) ctx.lookup("java:ConnectDaily");
conn = ds.getConnection();
if(committeeCode != null){
//get all events
String queryStatement = "SELECT " +
.......
"WHERE c.calendar_id = ci.calendar_id AND c.short_name LIKE ? " +
"AND ci.style_id = 0 " +
"AND ci.starting_date > to_char(sysdate-1, 'J') " +
"AND ci.item_type_id = cit.item_type_id " +
"ORDER BY to_date(to_char(ci.starting_date), 'J')";
ps = conn.prepareStatement(queryStatement);
ps.setString(1, "'%" + committeeCode + "%'");
System.out.println(queryStatement);
rs = ps.executeQuery();
if (rs != null){
while(rs.next()){
String com = rs.getString("name");
String comID = rs.getString("short_name");
String startTime = rs.getString("starting_time");
String endTime = rs.getString("ending_time");
String name = rs.getString("contact_name");
String desc = rs.getString("description");
String info = rs.getString("contact_info");
String date = rs.getString("directory");
htmlBuilder.append("<li><a href='?com="+committeeCode+"&directory=2014-09-10'>"+com+" - "+ date +" - "+startTime+" - "+endTime+"</a> <!-- Link/title/date/start-end time --><br>");
htmlBuilder.append("<strong>Location: </strong>"+comID+"<br>");
htmlBuilder.append("<strong>Dial-In:</strong>"+com+"<br>");
htmlBuilder.append("<strong>Part. Code:</strong>"+info+"<br>");
htmlBuilder.append("<a href='http://nyiso.webex.com'>Take me to WebEx</a>");
htmlBuilder.append("</li>");
}
}
html = htmlBuilder.toString();
.
.
.
}catch (NamingException e) {
e.printStackTrace();
//log error and send error email
} catch (SQLException e) {
e.printStackTrace();
//log error and send error email
}finally{
//close all resources here
ps.close();
rs.close();
conn.close();
}
return html;
}
}
Output
14:18:22,979 INFO [STDOUT] SELECT to_char(to_date(to_char(ci.starting_date), 'J'),'mm/dd/yyyy') as start_date, to_char(to_date(to_char(ci.ending_date), 'J'),'mm/dd/yyyy') as end_date, to_char(to_date(to_char(ci.starting_date), 'J'),'yyyy-mm-dd') as directory, ci.starting_time, ci.ending_time, ci.description, cit.description as location, c.name, c.short_name, ci.add_info_url, ci.contact_name, ci.contact_info FROM calitem ci, calendar c, calitemtypes cit WHERE c.calendar_id = ci.calendar_id AND c.short_name LIKE ? AND ci.style_id = 0 AND ci.starting_date > to_char(sysdate-1, 'J') AND ci.item_type_id = cit.item_type_id ORDER BY to_date(to_char(ci.starting_date), 'J')

There is no need for the quotes in setString:
ps.setString(1, "%" + committeeCode + "%");
This method will bind the specified String to the first parameter. It will not change the original query String saved in queryStatement.

The placeholder remains as part of the SQL text.
The bind value is passed when the statement is executed; the actual SQL text is not modified. (This is one of the big advantages of prepared statements: the same exact SQL text is reused, and we avoid the overhead of a hard parse.
Also note that you are including single quotes within the value, which is a bit odd.
If the bind placeholder were to be replaced in the SQL text, assuming committeeCode contains foo, the equivalent SQL text would be:
AND c.short_name LIKE '''%foo%'''
which will match only c.short_name values that begin and end with a single quote, and contain the string foo.
(This looks more like Oracle SQL syntax than it does MySQL.)

As we know that in setString we can pass string value only, So even if we write the code like this:
String param="'%"+committeeCode+"%'";
And if you print the value of param it will throw error, Hence you cannot use it as well in prepared statement.
You need to modify modify it little bit as:
String param="%"+committeeCode+"%";(Simpler one, other way can be used)
ps.setString(1,param);

How to get a particular column's values alone?

I am using the mysql java connector. I need java to display the contents of the first column and the second column in different steps. How do I achieve this?
String qry = "select col1,col2 from table1";
Resultset rs = statement.executeQuery(qry);

I've posted a sample below:
Statement s = conn.createStatement ();
s.executeQuery ("SELECT id, name, category FROM animal");
ResultSet rs = s.getResultSet ();
int count = 0;
while (rs.next ())
{
int idVal = rs.getInt ("id");
String nameVal = rs.getString ("name");
String catVal = rs.getString ("category");
System.out.println (
"id = " + idVal
+ ", name = " + nameVal
+ ", category = " + catVal);
++count;
}
rs.close ();
s.close ();
System.out.println (count + " rows were retrieved");
(From: http://www.kitebird.com/articles/jdbc.html#TOC_5 )
Edit: just re-read the question and think you might mean you want to refer to a column later on in code, instead of in the inital loop as in my example above. In that case, you can create an array and refer to the array later on, or, as another answer suggests you can just do another query.

Load them into any data structure of your choice and then display them to your heart's content.
List<String> firstCol = new ArrayList<String>();
List<String> secondCol = new ArrayList<String>();
while(rs.next()){
firstCol.add(rs.getString("col1"));
secondCol.add(rs.getString("col2"));
}
Then you can manipulate with the two list as you want.

How about ... (insert drumroll here):
String qry1 = "select col1 from table1";
Resultset rs1 = statement.executeQuery(qry);
String qry2 = "select col2 from table1";
Resultset rs2 = statement.executeQuery(qry);
(You might want to phrase your question more clearly.)

You can do it like this :
String sql = "select col1,col2 from table1";
ResultSet rs = stmt.executeQuery(sql);
while (rs.next()) System.out.println(rs.getString("col1"));

I am using following Code:
Statement sta;
ResultSet rs;
try {
sta = con.createStatement();
rs = sta.executeQuery("SELECT * FROM TABLENAME");
while(rs.next())
{
Id = rs.getString("COLUMN_Name1");
Vid = rs.getString("COLUMN_Name2");
System.out.println("\n ID : " + Id);
System.out.println("\n VehicleID: " + Vid);
}
}
catch(Execption e)
{
}
And this code is 100% working.

String emailid=request.getParameter("email");
System.out.println(emailid);
rt=st.executeQuery("SELECT imgname FROM selection WHERE email='emailid'");
System.out.println(rt.getString("imgname"));
while(rt.next())
{
System.out.println(rt.getString("imgname"));
finalimage=rt.getString("imgname");
}