Develop Reference

Working on this Java project where I need to be able to delete data from the database on user's request

The query inside MySQL is working:
DELETE FROM f9.yoo
WHERE account_tags = '#8GGGJPUR9'
I can delete data inside MySQL, but the problem is whenever I try to remove the account_tags from my Java application, it throws an error:
java.sql.SQLSyntaxErrorException: 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 'DELETE FROM f9.yoo
WHERE account_tags = '#8GGGJPUR9'' at line 2
Here's my Java SQL query:
Statement statement = dbConnection.createStatement();
String sql = "SELECT * FROM "+databaseName+"."+tableName+";\n" +
"DELETE FROM "+databaseName+"."+tableName+"\n" +
"WHERE account_tags = '"+AccountTag+"';";
statement.executeQuery(sql);
The error isn't giving me much to work with, so I really have no idea what is wrong with the program.

Did you add the allowMultiQueries=true
If not then you can add that while you sending the connecting request to your database. So you need to append the allowMultiQueries=true in your to database URL.
Like this:
String dbUrl = "jdbc:mysql:///test?allowMultiQueries=true";

String sql = "DELETE FROM "+databaseName+"."+tableName+"\n" +
"WHERE account_tags = ?";
try (PreparedStatement statement = dbConnection.prepareStatement(sq)) {
statement.setString(1, AccountTag);
int updateCount = statement.executeUpdate();
System.out.printf("%s: %d records deleted.%n", tableName, updateCount);
}
The only thing used is the DELETE, for which one should use executeUpdate.
One definitely should use a PreparedStatement as many code checkers will give alarms otherwise. It escapes things like ', handles types of the arguments, and possible conversions, and especially is a security feature against SQL injection.
The System.out usage is bad style, better would be using a logger.
try-with-resources automatically closes the PreparedStatement even with a raised exception or break/return.
When doing both database operations, it seems better to use two (prepared) statements, as the first returns a ResultSet.
So:
String sql = SELECT * FROM "+databaseName+"."+tableName + "\n" +
"WHERE account_tags = ?";
try (PreparedStatement statement = dbConnection.prepareStatement(sq)) {
statement.setString(1, AccountTag);
try (ResultSet rs = statement.executeQuery()) {
...
}
}

Better to separate statements with an If condition :
String sql1="SELECT * FROM "+databaseName+"."+tableName;
String sql2="DELETE FROM "+databaseName+"."+tableName+" "+
"WHERE account_tags = '"+AccountTag+"';
statement.executeQuery(sql1);
statement.executeUpdate(sql2);

How to use 2 JDateChooser as a searching tool in JTable?

I'm having problem with showing database values in my Jtable. I don't know how to use JDataChooser as a searching tool in JTable. I want the process like this, if JDateChooser1 is select to 08-17-2017 and JDateChooser2 is select 09-17-2017
the JTable will only show the values that having that date between 08-17-2017 - 09-17-2017. The format of the Date is (MM-dd-yyyy).
I have this method and as a testing I put the method to a button. I also want to know where I can put this method to be able not using a button. Auto search when I'm done selecting the dates.
sales is my table name in mysql and Date is the column name.
private void Dated() {
try {
String value1, value2;
value1 = jDateChooser1.getDate().toString();
value2 = jDateChooser2.getDate().toString();
String sql = "select * from sales where Date = '" + value1 + "' and '" + value2 + "'";
pst = conn.prepareStatement(sql);
rs = pst.executeQuery();
} catch (Exception e) {
JOptionPane.showMessageDialog(null, e);
}
}

You are missing some information in your query :
show the values that having that date between 08-17-2017 - 09-17-2017 you have to use between keyword in the query should be select * from sales where Date between date1 and date1 and not =
because you are using prepapred statement don't use concatination of the query and values.
beside Date is reserved keyword in MySQL instead you have to put it between two ``
Your code should look like :
Date value1 = jDateChooser1.getDate();
Date value2 = jDateChooser2.getDate();
String sql = "select * from sales where `Date` between ? and ?";
pst = conn.prepareStatement(sql);
pst.setDate(1, value1);
pst.setDate(2, value2);
rs = pst.executeQuery();

Using PrepareStatement to get data with configurable table name

I'm trying to get some data from Oracle 11.2 using java and jdbc driver.
My goal is to get data from database using CallableStatement, but with no luck - I'm not able to put table name as parameter. I would like to have configurable table name in query. However, it would be good to keep it sanitized.
Here is an example..
public void getData() throws SQLException {
Connection conn = Config.getSQLConnection();
String query = "SELECT * FROM ?";
PreparedStatement st = conn.prepareStatement(query);
st.setString(1, Config.DATATABLE_NAME);
ResultSet rs = st.executeQuery();
if (rs.next()) {
System.out.println("SUCCESS");
System.out.println("ID:" + rs.getString("ID"));
} else {
System.out.println("FAILURE");
}
}
Is this the way it should work? Or am I missing something, or misused it?

A CallableStatement is used to make call to stored procedures.
From javadoc:
The interface used to execute SQL stored procedures
Use a PreparedStament instead for a normal select.
As an additional note don't pass the name of the table as parameter.
Create the query using concatenation.
Instead of
String query = "SELECT * FROM ?";
use
String query = "SELECT * FROM " + Config.DATATABLE_NAME;

You should use PreparedStatement instead of CallableStatement.
CallableStatement is an interface which is used to call stored procedures.

MySQL Query in Java Eclipse

I am writing a program, where the user will be receiving instructions in different languages. I have the tables structures by language, so based on the user's language user settings, the corresponding language table will be selected. However, I keep getting errors from the following code.
String query2 = "select * from ? where instruction_id = ?";
PreparedStatement pst2 = connection.prepareStatement(query);
pst2.setString(1, user_config.language);
pst2.setString(2, instruction_id);
ResultSet rs2 = pst2.executeQuery();
Can someone explain why the above code is not working?

I ended up using string concatenation for the table name.
String query2 = "select * from " + user_config.language + " where instruction_id = ?";
PreparedStatement pst2 = connection.prepareStatement(query2);

SQLite select from LIKE statement not working?

When I view the database and run this query I get results as expected.
SELECT * FROM users WHERE options LIKE '%[-15,-3]%';
However when I use a prepared statement as seen below, the uuid is null.
String opt = "[-15,-3]"; //example
PreparedStatement ps = SQLite.connection.prepareStatement(
"SELECT * FROM users WHERE options LIKE '%" + opt + "%'"
);
ResultSet rs = ps.executeQuery();
String uuid = null;
while (rs.next()){
uuid = rs.getString("member");
}
rs.close();
ps.close();
if(uuid != null){
System.out.println("not null: " + uuid);
return Database.getUser(UUID.fromString(uuid);
}
For the code above, nothing is returned in the result set. Which is very strange because I used the same query with an SQLite viewer and it returned the proper rows. How can I solve this? I don't see an issue.
UPDATE
When I directly use "SELECT * FROM factions WHERE claims LIKE '%[-15,-3]%'" in the prepared statement instead of the variable, it works fine. Why can't I use a string variable? I've checked the variable and it prints to console fine.

I solved it after a lot of trial and error, turns out I should've been using a ? and set the string.
PreparedStatement ps = SQLite.connection.prepareStatement(
"SELECT * FROM users WHERE options LIKE ?"
);
ps.setString(1, "%" + opt + "%");