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SQLite Query With Parameters Not Working in Java

I have a program that selects from a database given a table and column string.
public void selectAllFrom(String table, String column){
String sql = "SELECT ? FROM ?";
try (Connection conn = this.connect();
PreparedStatement pstmt = conn.prepareStatement(sql)){
pstmt.setString(1, column);
pstmt.setString(2, table);
ResultSet rs = pstmt.executeQuery();
while (rs.next()){
System.out.println(rs.getString(column));
}
} catch (SQLException e){
System.out.println(" select didn't work");
System.out.println(e.getMessage());
}
}
For some reason it is not working and it is going right to catch
Here is the connect() function as well:
private Connection connect(){
Connection conn = null;
// SQLite connection string
String url = "jdbc:sqlite:C:/sqlite/db/chinook.db";
try{
// creates connection to the database
conn = DriverManager.getConnection(url);
System.out.println("Connection to SQLite has been established");
} catch (SQLException e){
System.out.println(e.getMessage());
System.out.println("Connection didn't work");
}
return conn;
}
I know the problem is not with the database because I'm able to run other select queries without parameters. It is the parameters that are giving me the problem. Can anyone tell what the problem is?

A table or column name can't be used as a parameter to PreparedStatement. It must be hard coded.
String sql = "SELECT " + column + " FROM " + table;
You should reconsider the design so as to make these two constant and parameterize the column values.

? is a place holder to indicate a bind variable. When a SQL statement is executed, database first checks syntax, and validates the objects being referenced, columns and access permission for specified objects (i.e metadata about objects) and confirms that all are in place and valid. This stage is called parsing.
Post parsing, it substitutes bind variables to query and then proceeds for actual fetch of results.
Bind variables can be substituted in any place in query to replace an actual hard coded data/strings, but not the query constructs them selves. It means
You can not use bind variables for keywords of sql query (ex: SELECT, UPDATE etc.)
You can not use bind variables for objects or their attributes (i.e table names, column names, functions, procedures etc.)
You can use them only in place of a otherwise hard coded data.
ex: SELECT FIRST_NAME, LAST_NAME, 'N' IS_DELETED FROM USER_DATA WHERE COUNTRY ='CANADA' AND VERIFIED_USER='YES'
In above sample query, 'N','CANADA' and 'YES' are the only strings which can be replaced by a bind variable, not any other word.
Using bind variable is best practice of coding. It improves query performance (when used with large no. of queries in tuned database products like Oracle or MSSQL) and also protects your code against sql injection attacks.
Constructing query by concatenating strings (especially data part of query) is never recommended way. You can still construct a query by concatenation for other parts like table name or column name as long as those strings are not directly taken from input.
Below example is acceptable:
query = "Select transaction_id, transaction_date from ";
if (isHistorical(reportType)
{ query = query + "HISTORY_TRANSACTIONS" ;}
else
{query = query + "PRESENT_TRANSACTIONS" ; }
recommended practice is to use
String query_present = "SELECT transaction_id, transaction_date from PRESENT_TRANSACTIONS";
String query_historical = "SELECT transaction_id, transaction_date from HISTORY_TRANSACTIONS";
if (isHisotrical(reportType))
{
ps.executeQuery(query_historical);
}else{
ps.executeQuery(query_present);
}

How to get all the rows affected by a UPDATE query in JDBC?

I have an assignment where I need to update records using a PreparedStatement. Once the record have been updated as we know update query return count, i.e., number of row affected.
However, instead of the count I want the rows that were affected by update query in response, or at least a list of id values for the rows that were affected.
This my update query.
UPDATE User_Information uInfo SET address = uInfo.contact_number || uInfo.address where uInfo.user_id between ? AND ?;
Normally it will return count of row affected but in my case query should return the ids of row or all the row affected.
I have used the returning function of PostgreSQL it is working but is not useful for me in that case.

i have used returning function of PostgreSQL but is not useful for me
It should be. Perhaps you were just using it wrong. This code works for me:
sql = "UPDATE table1 SET customer = customer || 'X' WHERE customer LIKE 'ba%' RETURNING id";
try (PreparedStatement s = conn.prepareStatement(sql)) {
s.execute(); // perform the UPDATE
try (ResultSet rs = s.getResultSet()) {
// loop through rows from the RETURNING clause
while (rs.next()) {
System.out.println(rs.getInt("id")); // print the "id" value of the updated row
}
}
}
The documentation indicates that we can also use RETURNING * if we want the ResultSet to include the entire updated row.
Update:
As #CraigRinger suggests in his comment, the PostgreSQL JDBC driver does actually support .getGeneratedKeys() for UPDATE statements too, so this code worked for me as well:
sql = "UPDATE table1 SET customer = customer || 'X' WHERE customer LIKE 'ba%'";
try (PreparedStatement s = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS)) {
s.execute(); // perform the UPDATE
try (ResultSet rs = s.getGeneratedKeys()) {
while (rs.next()) {
System.out.println(rs.getInt(1)); // print the "id" value of the updated row
}
}
}
Thanks, Craig!

You might be able to use JDBC's support for getting generated keys. See the Connection.prepareStatement(String sql, int[] columnIndexes) API method, then use Statement.getGeneratedKeys() to access the results.
The spec says "the driver will ignore the array if the SQL statement is not an INSERT statement" but I think PostgreSQL's JDBC driver will actually honour your request with other statement types too.
e.g.
PreparedStatement s = conn.prepareStatement(sql, new String[] {'id'})
s.executeUpdate();
ResultSet rs = s.getGeneratedKeys();
Otherwise, use RETURNING, as Gord Thompson describes.

There are two way of doing it
1. by passing an array of column name or index of column prepareStatement
i.e conn.prepareStatement(sql, new String[] {'id','uname'})
and
2. by using Statement.RETURN_GENERATED_KEYS in prepareStatement.
My code is for this i.e as per my requirement i have developed my code you can have a look for better idea.
private static final String UPDATE_USER_QUERY= "UPDATE User_Information uInfo SET address = uInfo.contact_number || uInfo.address where uInfo.user_id between ? AND ?;";
//pst = connection.prepareStatement(UPDATE_USER_QUERY,columnNames);
pst = connection.prepareStatement(UPDATE_USER_QUERY,Statement.RETURN_GENERATED_KEYS);
ResultSet rst = pst.getGeneratedKeys();
List<UserInformation> userInformationList = new ArrayList<UserInformation>();
UserInformation userInformation;
while (rst.next()){
userInformation = new UserInformation();
userInformation.setUserId(rst.getLong("user_id"));
userInformation.setUserName(rst.getString("user_name"));
userInformation.setUserLName(rst.getString("user_lName"));
userInformation.setAddress(rst.getString("address"));
userInformation.setContactNumber(rst.getLong("contact_number"));
userInformationList.add(userInformation);
}
That think i need to achieve in this case.
Hope so this will help you a lot.

Getting inserted (or existing) ids with executeBatch()

I am trying to insert some words to database and return newly inserted id or existing id if the word is already in the database.
I found that I can do this using PreparedStatement and including Statement.RETURN_GENERATED_KEYS. But PreparedStatement is terribly slow. I need to insert like 5000 words at once. Another way I could achieve it by running individual query in for loop:
public ArrayList<Integer> addWords(ArrayList<String[]> allTermsForTag) {
ArrayList ids = new ArrayList<Integer>();
ResultSet rs = null;
try{
Statement st = connection.createStatement();
for (String[] articleTerms: allTermsForTag) {
for(String term: articleTerms) {
String query = "WITH a AS (INSERT INTO tag (name) SELECT '"+term+"' WHERE NOT EXISTS (SELECT name FROM tag WHERE name = '"+term+"') " +
"RETURNING id) SELECT id FROM a UNION SELECT id FROM tag WHERE name = '"+term+"'";
rs = st.executeQuery(query);
while (rs.next())
{
int id = rs.getInt(1);
ids.add(id);
System.out.printf("id: "+id);
}
}
}
rs.close();
st.close();
}catch(SQLException e){
System.out.println("SQL exception was raised while performing SELECT: "+e);
}
return ids;
}
This does what I need nicely, but this is too slow as well.
Another method that I wrote uses executeBatch(), however, it does not return ids:
public ArrayList<Integer> addWords(ArrayList<String[]> allTermsForTag){
ResultSet rs = null;
ArrayList ids = new ArrayList<Integer>();
try{
Statement st = connection.createStatement();
for (String[] articleTerms: allTermsForTag) {
for(String term: articleTerms) {
String query = "WITH a AS (INSERT INTO tag (name) SELECT '"+term+"' WHERE NOT EXISTS (SELECT name FROM tag WHERE name = '"+term+"') " +
"RETURNING id) SELECT id FROM a UNION SELECT id FROM tag WHERE name = '"+term+"'";
st.addBatch(query);
}
st.executeBatch();
rs = st.getGeneratedKeys();
while (rs.next()) {
int id = rs.getInt(1);
ids.add(id);
}
}
st.close();
return ids;
}catch (SQLException e){
System.out.println("SQL exception was raised while performing batch INSERT: "+e.getNextException());
System.out.println("dub");
}
return null;
}
So the question is - how to get ids when using executeBatch() or if this is not possible, how to approach this problem? I need it to work as fast as possible, because there will be a lot of INSERT operations with large amount of data.
Thank you!

Set set = new HashSet();
try {
PreparedStatement ps = cn.prepareStatement("delete from myTable where... ",
Statement.RETURN_GENERATED_KEYS);
ps.setInt(1,200);
ps.setInt(2,262);
ps.setString(3, "108gf99");
ps.addBatch();
ps.setInt(1,200);
ps.setInt(2,250);
ps.setString(3, "hgfha");
ps.addBatch();
ps.executeBatch();
ResultSet rs = ps.getGeneratedKeys();
while (rs.next()){
set.addAll(Collections.singleton(rs.getLong(1)));
}
System.out.println(set);
} catch (SQLException e) {
e.printStackTrace();
}

executeBatch can return generated keys in the latest PgJDBC versions. See issue 195 and pull 204. You must use the prepareStatement variant that takes a String[] of returned column names.
However... take a step back here. The solution isn't loops. The solution is almost never loops.
In this case, you should almost certainly use COPY via the PgJDBC CopyManager API to COPY data into a TEMPORARY table. Then do an INSERT INTO ... SELECT ... RETURNING ... to insert the temp table's contents into the final table and return any generated fields. You can also do a SELECT to join on the temp table to return any that already exist. This is basically a bulk upsert or closely related bulk insert-if-not-exists.
If for some reason you can't do that, the next-best option is probably multi-valued INSERTs with large VALUES lists, but this requires some ugly dynamic SQL. Since you need existing values if the row already exists you'll probably need a writeable CTE too. So really, just use COPY and a query to do the table merge.

GemfireXD - PreparedStatement setArray for String(VARCHAR) array not working

I have some JDBC code as follows where I am using gemfireXD as DB.
I am trying to parallelize the execution of a procedure on a list of inputs. The size of the list I am passing as the parameter to the procedure is not fixed and it is determined after the execution of the query in the code below. This list can be too big in size.
Code:
private static void executeProc (Connection cxn) throws SQLException {
Statement stmt = null;
try {
stmt = cxn.createStatement();
stmt.execute("select distinct field1 from Table1");
ResultSet rs = stmt.getResultSet();
List<String> fieldList = new ArrayList<String> ();
while (rs.next()) {
fieldList.add(rs.getString("field1"));
}
Array fieldArray = cxn.createArrayOf("VARCHAR", fieldList.toArray(new String[fieldList.size()]));
CallableStatement callableStmt = cxn.prepareCall("{CALL procedure1() ON TABLE Table1 WHERE field1 IN (?)}");
callableStmt.setArray(1, fieldArray);
callableStmt.execute();
} catch (SQLException e) {
e.printStackTrace();
}
}
Error:
while executing the code it is giving below runtime error.
Feature not Implemented : createArrayOf(String, Object[])
Question:
The gemfireXD documentation says Data Aware procedure can be executed passing a list using setArray method. But when I am working on actual API, the setAaary() method is expecting an Array Object instead of a List.
GemfireXD document gives an example of such procedure call in its documentation (1.4.0) which supports setArray() method. The direct example from the documentation is as follows: -
// GemFire XD data-aware procedure invocation.
CallableStatement callableStmt = connection.prepareCall("{CALL order_credit_check() ON TABLE Orders WHERE customerID IN (?)}");
callableStmt.setArray(1, <-list of customer IDs->);
How do I call preparedStatement.setArray to set the parameter in the query?
Could any one please suggest any other implementation approch to achieve the desired result?

GemFire XD does not support Array data type so createArrayOf method will not work.
For the kind of query in you question where you want to use in-list in the where clause, you may have to set each individual value as a parameter
CallableStatement callableStmt = cxn.prepareCall("{CALL procedure1() ON TABLE Table1 WHERE field1 IN (?, ?, ?)}");
callableStmt.setInt(1, 1);
callableStmt.setInt(2, 2);
callableStmt.setInt(3, 3);
....

JAVA Writing to Access database and retrieving and index

I'm writing data from Java to an Access database on Windows 32 bit. When I write a record, I need to retrieve the row ID / primary key so that I can a) update the record easily if I want to and b) cross reference other data to that record.
When did something similar in C, I could make a updatable cursor which allowed me to write a new record and simultaneously retrieve the row ID. With Java, it looks as though I should be able to do this, but it throws an exception with the following code.
con = openAccessDatabase();
String selectString = "SELECT ID, RunCount FROM SpeedTable";
try {
PreparedStatement selectStatement = con.prepareStatement(selectString,
ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_UPDATABLE);
ResultSet idResult = selectStatement.executeQuery();
int id;
for (int i = 0; i < nWrites; i++) {
idResult.moveToInsertRow();
idResult.updateObject(1, null); // this line makes no difference whatsoever !
idResult.updateInt(2, i);
idResult.insertRow(); // throws java.sql.SQLException: [Microsoft][ODBC Microsoft Access Driver]Error in row
id = idResult.getInt(1);
}
selectStatement.close();
} catch (SQLException e) {
e.printStackTrace();
}
The only thing I've been able to do is to write a new record and then run a different query to get the Row id back ...
String insertString = "INSERT INTO SpeedTable (RunCount) VALUES (?)";
String idString = "SELECT ID FROM SpeedTable ORDER BY ID DESC";
//
try {
ResultSet idResult = null;
PreparedStatement preparedStatement, idStatement;
preparedStatement = con.prepareStatement(insertString,
ResultSet.TYPE_FORWARD_ONLY,
ResultSet.CONCUR_READ_ONLY);
idStatement = con.prepareStatement(idString,
ResultSet.TYPE_FORWARD_ONLY,
ResultSet.CONCUR_READ_ONLY);
for (int i = 0; i < nWrites; i++) {
// write the data into the database
preparedStatement.setInt(1, i);
preparedStatement.execute();
// re-run the query to get the index back from the database.
idResult = idStatement.executeQuery();
idResult.next();
int lastIndex = idResult.getInt(1);
idResult.close();
}
This works but becomes impossibly slow when the table has more than a few 10's of 1000's of records in it. There is also a risk of returning the wrong ID if two parts of the program start writing at the same time (unlikely but not impossible).
I know that at least one suggestion will be to either not use Java or not use Access, but they are not options. It's also part of a free open source software package, so I'm reluctant to pay for anything. Writing my own C JNI interface which provides the basic functionality that I need for my application is even less appealing.

Not sure if this works for MS Access but you can try:
st.executeUpdate("INSERT INTO SpeedTable (RunCount) VALUES (1000)", Statement.RETURN_GENERATED_KEYS);
ResultSet rs = st.getGeneratedKeys();
rs.next();
long id = rs.getLong(1);