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Java SQL Update Query Not Working

I'm working on a simple java project that uses JavaDB and MySQL to introduce the use of databases. I'm trying to write a method for updating the scores of a game in a database.
public void setTeamsScore(int matchNumber, int hScore, int vScore) throws SQLException
{
Statement stmt = connection.createStatement();
String sqlStatement = "UPDATE Matches " +
"SET HomeTeamScore = " + hScore +
" WHERE " +
"MatchNumber = " + matchNumber;
stmt.executeUpdate(sqlStatement);
sqlStatement = "UPDATE Matches " +
"SET VisitorTeamScore = " + vScore +
" WHERE " +
"MatchNumber = " + matchNumber;
stmt.executeUpdate(sqlStatement);
}
I get no errors at runtime, and when I check the return value of the update statement, it returns 1 (which if I understand correctly, means that 1 row was updated in the database). However, the database doesn't get updated at all and keeps the same values from before.
At first, I thought that maybe auto-commit wasn't working, so I tried turning auto-commit off and using connection.comit() but that didn't solve the problem either.
Any guidance would be much appreciated.

First of all you have to check if the Auto-commit is set to true or false .
if false then you have to commit the connection after the SQL execution .
int rows = stmt.executeUpdate(sqlStatement);
System.out.println("Rows impacted : " + rows );
stmt.commit();
stmt.close();

You need to call both stmt.execute(sql) and stmt.executeUpdate(sql)
First check if your query returns a true result set or not.
Boolean ret = stmt.execute(sqlStatement);
Then update the records
int rows = stmt.executeUpdate(sqlStatement);
System.out.println("Rows impacted : " + rows );
If the data is still not updated check your connection object.

MySQL query not working in Java

String sqlInsertBeacon = "INSERT INTO `beacon` (zone_id, location) VALUE ('(SELECT id FROM zone WHERE GeographicalID = '" + geometry3 + "')', Point(" + x_coordinate + "," + y_coordinate + "))";
System.out.println("The SQL query is: " + sqlInsertBeacon); // Echo for debugging
int countInserted3 = stmt.executeUpdate(sqlInsertBeacon);
System.out.println(countInserted3 + " records inserted.\n");
When I run the above code, the build is successful but the program stops when it reaches the execute line. I am entering using this sql query to insert data into a mysql database. I am not sure where the error is in my query? Can anyone suggest an alternative way or find the mistake?
The output of the program is this, as you can see the program, stops running after the second line:
The SQL query is: INSERT INTO table
(zone_id, location)
VALUES
((SELECT id FROM zone WHERE GeographicalID = '6311599'), Point(-121.9453802,37.3256131) )
;
BUILD SUCCESSFUL (total time: 6 seconds)
For additional information incase it helps:
The stmt, is created like this:
try (
// Step 1: Allocate a database 'Connection' object
Connection conn = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/adhwere2?useSSL=false", "root", "your_new_password"); // MySQL
// Step 2: Allocate a 'Statement' object in the Connection
Statement stmt = conn.createStatement();) {
and the catch exception is :
} catch (SQLException ex) {
}

Try something like this:
String sqlInsertBeacon = "INSERT INTO `beacon` (zone_id, location)" +
" VALUES ( (SELECT id FROM zone WHERE GeographicalID = '" + geometry3 + "'), Point(" +
x_coordinate + "," + y_coordinate + "))";
Just removed the apostrophes aroung the inner SELECT and replaced VALUE with VALUES...

The problem was because the sub-query was returning more than one result, and printing out a stack trace helped debug this error. Using Limit 1 in the sub query also solved this issue.

please use query according to this syntax:
INSERT INTO table
(column1, column2, ... )
VALUES
(expression1, expression2, ... ),
(expression1, expression2, ... ),
...;
your table name is in single quotes and its VALUES not value mind these small things

Correct INSERT INTO SELECT statement looks like this:
INSERT INTO table2
SELECT * FROM table1
WHERE condition;
And you can use PreparedStatement to set parameters in your query.

Sql2o keep returning a same set of data although query is different

I am new to using SQL2O with MySQL, but I am having a weird problem, where different queries return same results. Is SQL2O returning me cached results?
My code looks like this:
String sql = "SELECT * " +
"FROM report_A" +
"ORDER BY :order :sequence "+
"LIMIT :from, :limit";
int limit = 5;
int startIndex = (page-1)*limit;
String sequence = "DESC";
try(Connection con = sql2o.open()) {
if(order.contains("-")){
order = order.replace("-", "");
sequence= " ASC";
}
Query query= con.createQuery(sql)
.addParameter("from", startIndex)
.addParameter("limit", limit)
.addParameter("order", order)
.addParameter("sequence", sequence);
List<ReportA> result = query.executeAndFetch(ReportA.class);
con.close();
The 4 parameters always change, but the output remains the same. I have verified the queries in mysql workbench, the data is different, but SQL2O returns me the same set of data. Am I missing something?

Your query is invalid. It wont compile and throw an Sql2oException on execution.
The problem is, basically, that you can use parameters only for values, not for table names, column names or other keywords like "ASC". Changing those would change the structure of the query.
It's possible to construct queries with variable structure by good old string concatenation, i.e.
String sql = "SELECT * " +
"FROM report_A" +
"ORDER BY " + order " " + SEQUENCE +
"LIMIT :from, :limit";
and then
query(sql)
.addParameter("from", from)
.addParameter("limit", limit)
.executeAndFetch(...)

Using a database API cursor with JDBC and SQLServer to select batch results

SOLVED (See answer below.)
I did not understand my problem within the proper context. The real issue was that my query was returning multiple ResultSet objects, and I had never come across that before. I have posted code below that solves the problem.
PROBLEM
I have an SQL Server database table with many thousand rows. My goal is to pull the data back from the source database and write it to a second database. Because of application memory constraints, I will not be able to pull the data back all at once. Also, because of this particular table's schema (over which I have no control) there is no good way for me to tick off the rows using some sort of ID column.
A gentleman over at the Database Administrators StackExchange helped me out by putting together something called a database API cursor, and basically wrote this complicated query that I only need to drop my statement into. When I run the query in SQL Management Studio (SSMS) it works great. I get all the data back, a thousand rows at a time.
Unfortunately, when I try to translate this into JDBC code, I get back the first thousand rows only.
QUESTION
Is it possible using JDBC to retrieve a database API cursor, pull the first set of rows from it, allow the cursor to advance, and then pull the subsequent sets one at a time? (In this case, a thousand rows at a time.)
SQL CODE
This gets complicated, so I'm going to break it up.
The actual query can be simple or complicated. It doesn't matter. I've tried several different queries during my experimentation and they all work. You just basically drop it into the the SQL code in the appropriate place. So, let's take this simple statement as our query:
SELECT MyColumn FROM MyTable;
The actual SQL database API cursor is far more complicated. I will print it out below. You can see the above query buried in it:
-- http://dba.stackexchange.com/a/82806
DECLARE #cur INTEGER
,
-- FAST_FORWARD | AUTO_FETCH | AUTO_CLOSE
#scrollopt INTEGER = 16 | 8192 | 16384
,
-- READ_ONLY, CHECK_ACCEPTED_OPTS, READ_ONLY_ACCEPTABLE
#ccopt INTEGER = 1 | 32768 | 65536
,#rowcount INTEGER = 1000
,#rc INTEGER;
-- Open the cursor and return the first 1,000 rows
EXECUTE #rc = sys.sp_cursoropen #cur OUTPUT
,'SELECT MyColumn FROM MyTable'
,#scrollopt OUTPUT
,#ccopt OUTPUT
,#rowcount OUTPUT;
IF #rc <> 16 -- FastForward cursor automatically closed
BEGIN
-- Name the cursor so we can use CURSOR_STATUS
EXECUTE sys.sp_cursoroption #cur
,2
,'MyCursorName';
-- Until the cursor auto-closes
WHILE CURSOR_STATUS('global', 'MyCursorName') = 1
BEGIN
EXECUTE sys.sp_cursorfetch #cur
,2
,0
,1000;
END;
END;
As I've said, the above creates a cursor in the database and asks the database to execute the statement, keep track (internally) of the data it's returning, and return the data a thousand rows at a time. It works great.
JDBC CODE
Here's where I'm having the problem. I have no compilation problems or run-time problems with my Java code. The problem I am having is that it returns only the first thousand rows. I don't understand how to utilize the database cursor properly. I have tried variations on the Java basics:
// Hoping to get all of the data, but I only get the first thousand.
ResultSet rs = stmt.executeQuery(fq.getQuery());
while (rs.next()) {
System.out.println(rs.getString("MyColumn"));
}
I'm not surprised by the results, but all of the variations I've tried produce the same results.
From my research it seems like the JDBC does something with database cursors when the database is Oracle, but you have to set the data type returned in the result set as an Oracle cursor object. I'm guessing there is something similar with SQL Server, but I have been unable to find anything yet.
Does anyone know of a way?
I'm including example Java code in full (as ugly as that gets).
// FancyQuery.java
import java.sql.*;
public class FancyQuery {
// Adapted from http://dba.stackexchange.com/a/82806
String query = "DECLARE #cur INTEGER\n"
+ " ,\n"
+ " -- FAST_FORWARD | AUTO_FETCH | AUTO_CLOSE\n"
+ " #scrollopt INTEGER = 16 | 8192 | 16384\n"
+ " ,\n"
+ " -- READ_ONLY, CHECK_ACCEPTED_OPTS, READ_ONLY_ACCEPTABLE\n"
+ " #ccopt INTEGER = 1 | 32768 | 65536\n"
+ " ,#rowcount INTEGER = 1000\n"
+ " ,#rc INTEGER;\n"
+ "\n"
+ "-- Open the cursor and return the first 1,000 rows\n"
+ "EXECUTE #rc = sys.sp_cursoropen #cur OUTPUT\n"
+ " ,'SELECT MyColumn FROM MyTable;'\n"
+ " ,#scrollopt OUTPUT\n"
+ " ,#ccopt OUTPUT\n"
+ " ,#rowcount OUTPUT;\n"
+ " \n"
+ "IF #rc <> 16 -- FastForward cursor automatically closed\n"
+ "BEGIN\n"
+ " -- Name the cursor so we can use CURSOR_STATUS\n"
+ " EXECUTE sys.sp_cursoroption #cur\n"
+ " ,2\n"
+ " ,'MyCursorName';\n"
+ "\n"
+ " -- Until the cursor auto-closes\n"
+ " WHILE CURSOR_STATUS('global', 'MyCursorName') = 1\n"
+ " BEGIN\n"
+ " EXECUTE sys.sp_cursorfetch #cur\n"
+ " ,2\n"
+ " ,0\n"
+ " ,1000;\n"
+ " END;\n"
+ "END;\n";
public String getQuery() {
return this.query;
}
public static void main(String[ ] args) throws Exception {
String dbUrl = "jdbc:sqlserver://tc-sqlserver:1433;database=MyBigDatabase";
String user = "mario";
String password = "p#ssw0rd";
String driver = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
FancyQuery fq = new FancyQuery();
Class.forName(driver);
Connection conn = DriverManager.getConnection(dbUrl, user, password);
Statement stmt = conn.createStatement();
// We expect to get 1,000 rows at a time.
ResultSet rs = stmt.executeQuery(fq.getQuery());
while (rs.next()) {
System.out.println(rs.getString("MyColumn"));
}
// Alas, we've only gotten 1,000 rows, total.
rs.close();
stmt.close();
conn.close();
}
}

I figured it out.
stmt.execute(fq.getQuery());
ResultSet rs = null;
for (;;) {
rs = stmt.getResultSet();
while (rs.next()) {
System.out.println(rs.getString("MyColumn"));
}
if ((stmt.getMoreResults() == false) && (stmt.getUpdateCount() == -1)) {
break;
}
}
if (rs != null) {
rs.close();
}
After some additional googling, I found a bit of code posted back in 2004:
http://www.coderanch.com/t/300865/JDBC/databases/SQL-Server-JDBC-Registering-cursor
The gentleman who posted the snippet that I found helpful (Julian Kennedy) suggested: "Read the Javadoc for getUpdateCount() and getMoreResults() for a clear understanding." I was able to piece it together from that.
Basically, I don't think I understood my problem well enough at the outset in order to phrase it correctly. What it comes down to is that my query will be returning the data in multiple ResultSet instances. What I needed was a way to not merely iterate through each row in a ResultSet but, rather, iterate through the entire set of ResultSets. That's what the code above does.

If you want all records from the table, just do "Select * from table".
The only reason to retrieve in chunks is if there is some intermediate place for the data: e.g. if you are showing it on the screen, or storing it in memory.
If you are simply reading from one and inserting to another, just read everything from the first.You will not get any better performance by trying to retrieve in batches. If there is a difference, it will be negative. Frame your query in a way that brings back everything. The JDBC software will handle all the other breaking-up and reconstituting that you need.
However, you should batch the update/insert side of things.
The set-up would create two statements on the two connections:
Statement stmt = null;
ResultSet rs = null;
PreparedStatement insStmt = null;
stmt = conDb1.createStatement();
insStmt = conDb2.prepareStament("insert into tgt_db2_table (?,?,?,?,?......etc. ?,?) ");
rs = stmt.executeQuery("select * from src_db1_table");
Then, loop over the select as normal, but use batching on the target.
int batchedRecordCount = 0;
while (rs.next()) {
System.out.println(rs.getString("MyColumn"));
//Here you read values from the cursor and set them to the insStmt ...
String field1 = rs.getString(1);
String field2 = rs.getString(2);
int field3 = rs.getInt(3);
//--- etc.
insStmt.setString(1, field1);
insStmt.setString(2, field2);
insStmt.setInt(3, field3);
//----- etc. for all the fields
batchedRecordCount++;
insStmt.addBatch();
if (batchRecordCount > 1000) {
insStmt.executeBatch();
}
}
if (batchRecordCount > 0) {
//Finish of the final (partial) set of records
insStmt.executeBatch();
}
//Close resources...

Creating a database table if it does not exist in Java production code and confirming in JUnit

I am writing a database program in Java and want to create a table if it does not already exist. I learned about DatabaseMetaData.getTables() from How can I detect a SQL table's existence in Java? and I am trying to use it:
private boolean tableExists() throws SQLException {
System.out.println("tableExists()");
DatabaseMetaData dbmd = conn.getMetaData();
ResultSet rs = dbmd.getTables(null, null, this.getTableName(), null);
System.out.println("TABLE_NAME: " + rs.getString("TABLE_NAME"));
return rs.getRow() == 1;
}
The problem is that rs.getRow() always returns 0, even after the table has been created. Using rs.getString("TABLE_NAME") throws an exception stating that the result set is empty.
One possible solution I thought of is to execute the CREATE TABLE statement and catch any exceptions that are thrown. However, I don't like the idea of using exceptions for control flow of my program.
FWIW, I am using HSQLDB. However, I would like write Java code that is independent of the RDMS engine. Is there another way to use DatabaseMetaData.getTables() to do what I want? Or is there some other solution to write my tableExists() method?
Added:
Using the suggestions given here, I found a solution that seems to work in my production code:
private void createTable() throws SQLException {
String sqlCreate = "CREATE TABLE IF NOT EXISTS " + this.getTableName()
+ " (brand VARCHAR(10),"
+ " year INTEGER,"
+ " number INTEGER,"
+ " value INTEGER,"
+ " card_count INTEGER,"
+ " player_name VARCHAR(50),"
+ " player_position VARCHAR(20))";
Statement stmt = conn.createStatement();
stmt.execute(sqlCreate);
}
Now I am also writing a JUnit test to assert that the table does indeed get created:
public void testConstructor() throws Exception {
try (BaseballCardJDBCIO bcdb = new BaseballCardJDBCIO(this.url)) {
String query = "SELECT count(*) FROM information_schema.system_tables WHERE table_name = '" + bcdb.getTableName() + "'";
Connection conn = DriverManager.getConnection(this.url);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(query);
Assert.assertTrue(rs.next());
Assert.assertEquals(1, rs.getInt(1));
Assert.assertFalse(rs.next());
}
}
This test fails on the assertEquals() with the following message:
FAILED: expected: <1> but was: <0>

The solution I found seems to work:
private void createTable() throws SQLException {
String sqlCreate = "CREATE TABLE IF NOT EXISTS " + this.getTableName()
+ " (brand VARCHAR(10),"
+ " year INTEGER,"
+ " number INTEGER,"
+ " value INTEGER,"
+ " card_count INTEGER,"
+ " player_name VARCHAR(50),"
+ " player_position VARCHAR(20))";
Statement stmt = conn.createStatement();
stmt.execute(sqlCreate);
}
I had to place the IF NOT EXISTS in the correct location in my SQL statement.

From the ResultSet definition at Java docs:
A ResultSet object maintains a cursor pointing to its current row of
data. Initially the cursor is positioned before the first row. The
next method moves the cursor to the next row, and because it returns
false when there are no more rows in the ResultSet object, it can be
used in a while loop to iterate through the result set.
So, you must always call the next() method otherwise getRow() will always return zero as the cursor is positioned before the first row.

There is build in mysql functionality for what you seek: http://dev.mysql.com/doc/refman/5.0/en/create-table.html
In short: Just append IF NOT EXISTS at the end of your table creation query.
Edit:
There is no general way of doing this. Most databases have an information_scheme table though, a query to determine the information could look like this:
SELECT count(*)
FROM information_schema.system_tables
WHERE table_schem = 'public' AND table_name = 'user';
This works with sqlite, mysql, msql, mariadb and postgres + probably a lot of others.

I don't know if this will necessarily help towards your goals, but when I ran into this problem using Python and MySQL, I just added a "Drop Table" statement before each "Create Table" statement, such that just running the script automatically deletes the existing table, and then rebuilds each table. That may not work for your needs, but it's one solution that I found successful for my similar problem.