We Keep Coding

Database query and Java

I'm studying at a project about the creation of simple web application.
I'm creating a webapp about an Hotel and I have a problem about the reservation of a room.
I have 3 kind of rooms and I want when someone book a room, another one can't book the same room in the same period.
The problem is about this kind of control.
I have write this code:
UPDATE CODE AFTER AN ANSWER
Statement st = con.createStatement();
Statement stmt = con.createStatement();
out.println("connection successfull");
int total = 0;
ResultSet rs3 = stmt.executeQuery( "SELECT COUNT(*) as total FROM reservation WHERE idRoom = '" + idRoom +
"' AND ('" + arrivaldate + "' >= arrivaldate AND '" + arrivaldate + "' <= departuredate) OR ('" + departuredate + "' >= arrivaldate "
+ "AND '" + departuredate + "' <= departuredate)");
rs3.next(); // You'll ever have only one row
total = rs3.getInt("total");
/* String query = "SELECT COUNT(*) FROM reservation WHERE idRoom = '" + idRoom +
"' AND ('" + arrivaldate + "' >= arrivaldate AND '" + arrivaldate + "' <= departuredate) OR ('" + departuredate + "' >= arrivaldate "
+ "AND '" + departuredate + "' <= departuredate)" ;
*/
// ResultSet rs2 = stmt.executeQuery(check);
out.println("<h1> Stringa check eseguito </h1>");
if( total > 0) { // THIS DOESN't WORK OF COURSE
response.sendRedirect("home.jsp");
}
else {
st.executeUpdate("insert into reservation (login,email,typeroom,idRoom,arrivaldate,departuredate)values ('"+login+"','"+email+"','"+typeroom+"','"+idRoom+"','"+arrivaldate+"','"+departuredate+"')");
}
But it doesn't work properly because it lets me to book the same room in the same data.
How can I do in your opinion? Thank you for your attention.

First, you totally ignore your total:
while(rs3.next()){
rs3.getInt("total");
}
Should be:
rs3.next(); // You'll ever have only one row
total = rs3.getInt("total");
And second, never ever use concatenations in your queries:
ResultSet rs3 = stmt.executeQuery( "SELECT COUNT(*) as total FROM reservation WHERE idRoom = '" + idRoom +
"' AND ('" + arrivaldate + "' >= arrivaldate AND '" + arrivaldate + "' <= departuredate) OR ('" + departuredate + "' >= arrivaldate "
+ "AND '" + departuredate + "' <= departuredate)");
Always use PreparedStatements instead:
PreparedStatement ps = stmt.prepareStatement( "SELECT COUNT(*) as total FROM reservation WHERE idRoom = ? AND (? >= arrivaldate AND ? <= departuredate) OR (? >= arrivaldate AND ? <= departuredate)");
int c = 0;
ps.setInt(++c, idRoom);
ps.setDate(++c, arrivaldate);
ps.setDate(++c, departuredate);
ps.setDate(++c, arrivaldate);
ps.setDate(++c, departuredate);
ResultSet rs = ps.executeQuery();
// And your usual code here

Error in linking mysql and netbeans data

I am working with mysql and Netbeans java for my school project. Whenever I try to register the details to the sql, I get this error My SqlSyntaxErrorException:Unknown Column " [the data in the text field] in 'field list'"
Here's my code:
int age = Integer.parseInt(AgeTF.getText());
String name=NameTF.getText();
String id=IDTF.getText();
String dob=DobTF.getText();
String address=AddressTF.getText();
try {
Class.forName("java.sql.Driver");
String database = "jdbc:mysql://localhost:3306/final";
Connection conn = DriverManager.getConnection(database, "root", "sanchit");
Statement stmt = conn.createStatement();
String sql = "insert into aadhar values ( '" + id + "', " + name + ", '" + dob + "' , '" + age + "' , '" + address + "' );" ;
stmt.executeUpdate(sql);
}
catch( Exception e){
JOptionPane.showMessageDialog(null,"" + e);
}
JOptionPane.showMessageDialog(this,"You have been registered!");
Please help.
Thanks

You didn't protect name with simple quotes :
Write '" + name + "' instead of " + name + "
String sql = "insert into aadhar values ( '" + id + "', '" + name + "', '" + dob + "' , '" + age + "' , '" + address + "' );" ;

Checking for usename in mysql ...If it exist then inserting into other table Otherwise the base table

Well i have the following table Table1 in MySQL workbench--
user_id int not null,autoincrement
movie _id int not null
movie_name varchar
user_name varchar
rating int
genre varchar
Now following is the insertion into database--
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(
"jdbc:mysql://localhost:XXXX/Recommendation1", "root",
"XXXXXXXXXXX");
Statement st = con.createStatement();
int i = st
.executeUpdate("insert into Table1(movie_Id,movie_name,user_name,rating,genre) values('"
+ movieId
+ "','"
+ mname
+ "','"
+ pname
+ "','" + ratingr + "','" + genre + "')");
out.println("Data is successfully inserted!");
} catch (Exception e) {
System.out.print(e);
Now what i want that,if there already exist a user_name with that value (pnmae),which i am entering it should not enter into my Table 1 or update,but it should enter into another table Table 2,The schema of table 2 is as following--
movie _id int not null
movie_name varchar
user_name varchar
genre varchar
For that what to use .How to use if -else condition
The following is what i am doing while checking for the username if it exists
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(
"jdbc:mysql://localhost:XXXX/Recommendation1", "root",
"wXXXXX");
Statement st = con.createStatement();
//Statement st2 = con.createStatement();
String SQL = "SELECT * from Table1 WHERE user_name ='" + pname
+ "' ";
ResultSet rs = st.executeQuery(SQL);
--if (rs.) { //What to put here
int j = st
.executeUpdate("insert into Table2(movie_Id,movie_name,user_name,genre) values('"
+ movieId
+ "','"
+ mname
+ "','"
+ pname
+ "','" + genre + "') ");
}
int i = st
.executeUpdate("insert into Table1(movie_Id,movie_name,user_name,rating,genre) values('"
+ movieId
+ "','"
+ mname
+ "','"
+ pname
+ "','" + ratingr + "','" + genre + "') ");
/* ResultSet rs = st1.executeQuery();
out.println("name is already there");
out.println("Data is successfully inserted!"); */
/* final String Query = "SELECT t1.user_Id from Table1 t1 JOIN Table2 t2 on t2.movie_Id = t1.movie_id WHERE t2.user_name = 'vishal'";
PreparedStatement st11 = con.prepareStatement(Query);
ResultSet rw = st11.executeQuery();
rw.last();
int id = rw.getInt("user_Id");
System.out.print("ID: " + id);*/
Thanks

Try this :-
boolean isUser=false;
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(
"jdbc:mysql://localhost:XXXX/Recommendation1", "root",
"wXXXXX");
Statement st = con.createStatement();
String SQL = "SELECT 1 from Table1 WHERE user_name ='"+ pname
+ "' ";
ResultSet rs = st.executeQuery(SQL);
isUser=rs.next();
Statement st2 = con.createStatement();
if (isUser) { //check the user is exist or not
int j = st2.executeUpdate("insert into Table2(movie_Id,movie_name,user_name,genre) values('"
+ movieId
+ "','"
+ mname
+ "','"
+ pname
+ "','" + genre + "') ");
}else{
int i = st2.executeUpdate("insert into Table1(movie_Id,movie_name,user_name,rating,genre) values('"
+ movieId
+ "','"
+ mname
+ "','"
+ pname
+ "','" + ratingr + "','" + genre + "') ");
}
Hope this will help you.

Sql statement Java between 2 tables and 2 values ( variables)

i am trying to do the following and it doesnt accept it.
String sql_eco = "select * from orders where EmployeeID=" +e_ID + " and CustomerID ="' + cu_ID + "'";
select from two tables and two values( variables)

Try this:
String sql_eco = "select * +
from orders +
where EmployeeID=" +e_ID + " and CustomerID ='" + cu_ID + "'";
^

Try, assuming CustomerID and EmployeeID are both Integer column type
String sql_eco = "select * from orders where EmployeeID=" +e_ID + " and CustomerID =" + cu_ID;

Use this. you have misplaced " for CustomerId
String sql_eco = "select * from orders where EmployeeID=" +e_ID + " and CustomerID ='" + cu_ID + "'";

values variable u wanna say something like this?
String sql_eco = "select * +
from orders +
where 1=1 ";
if(e_ID != null) {
sql_eco += " AND EmployeeID=" +e_ID ;
}
if(cu_ID != null){
sql_eco += " and CustomerID ='" + cu_ID + "'";
}
to improve this code u can use stringbuilder/stringbuffer

JDBC delete statement with multiple columns

It says I ended this statement wrong when if I input it into sql plus with just the addition of ; it works perfectly. What am I doing wrong?
Statement statement = connection.createStatement();
statement.executeUpdate("delete from aplbuk MODEL = '"+ textField_4.getText() + "'AND year = '" + textField_1.getText() + "' AND Litres = '" + textField_2.getText()
+ "' AND ENGINE_TYPE = '" + textField_3.getText() + "'");
statement.close();

Keyword where is missing after table name aplbuk in your query delete from aplbuk MODEL.
Update the query as:
statement.executeUpdate("delete from aplbuk where MODEL = '"+
textField_4.getText() + "'AND year = '" +
textField_1.getText() + "' AND Litres = '" +
textField_2.getText() + "' AND ENGINE_TYPE = '" +
textField_3.getText() + "'");
Also if year and Litres are numeric fields then don't enclose the value in single quotes.