We Keep Coding

How to search and copy information from two tables in SQLite on Java?

Beginner here.
I have this problem: I have two tables in my database. Table Customers and table Parcels. The program should find a customers id number from table Customers, when the user types the customers name. Then copy the customers id to table Parcels under column "customer_id".
Here is what I have done, but NetBeans gives me the Index out of bound exception. I have also tried another way, but then the program thinks I am trying to access a column by the name of the users feed. (I have created the tables in another if clause) What should I do differently? Here is my code:
} if (feed.equals("4")) {
System.out.println("Add tracking number: ");
String tn = input.nextLine();
PreparedStatement a = db.prepareStatement("INSERT INTO Parcels(tracknumb,cust_id) VALUES(?,?)", Statement.RETURN_GENERATED_KEYS);
a.setString(1, u);
System.out.println("Add customer name: ");
String nameid = input.nextLine();
PreparedStatement y = db.prepareStatement("SELECT id FROM Customers WHERE name= ?");
y.setString(2, nameid);
ResultSet rl = y.executeQuery(nameid);
if(rl.next()) {
int id = rl.getInt(nameid);
a.setInt(2, id);

I'm pretty sure the problem is within your SQL requests.
You're trying to insert ? into one of your values in the database, but keep in mind that ? is something unknown to the SQLite database.
If you're trying to insert an empty value, insert NULL. If you're trying to insert something from somewhere else, try {0}, and add , yourValue.
Try this out and see if it works.
Note: If you still want to use questions marks within your database, type \"?\" or '?'. This way, if you've configured your table to use strings or chars, this will work.

Get current sequence Id to store in other tables

We have multiple tables and all are related with first table's primary key (example: id). Id is configured as a sequence and while inserting data into to first table we are using sequence.nextval in the insert query.
Now while inserting data to other tables, how to get current sequence value or current Id.
We have tried below options:
sequence.currval, directly in the insert statement
2.select sequence.currval from dual
Above two options throwing error while using getJdbcTemplate().update().
Could anyone please suggest how to get current sequence value to pass to other tables after inserting data into first table??

If you want to insert the same id (which comes from a sequence) to different tables, simple get it form the first insert and use it in the other inserts.
PrepearedStatement stmt1 = conn.prepareStatement("INSERT INTO TABLE1 (id) VALUES(yoursequence.nextval)", Statemet.RETURN_GENERATED_KEYS);
stmt1.executeUpdate();
ResultSet rs = stmt1.getGeneratedKeys();
rs.next();
long id = rs.getLong(1);
PrepearedStatement stmt2 = conn.prepareStatement("INSERT INTO TABLE2 (id) VALUES(?)");
stmt2.setLong(1,id);
stmt2.executeUpdate();

Insert only if row doesn't exist

I am using PreparedStatement to prepare sql queries. I want to insert a row in table if and only if it doesn't exist.
I tried this -
INSERT INTO users (userId) VALUES (?) ON DUPLICATE KEY UPDATE userId = ?
But this will unnecessarily update the userId.
How can i insert the userId here ?

INSERT INTO users
(userId)
SELECT ?
WHERE NOT EXISTS
(
SELECT *
FROM users
where userId = ?
)

You may use
INSERT IGNORE INTO users (userId) VALUES (?)
But you should understand why do you want ignore errors.

on duplicate key does not work correctly when the table is an innodb. It creates exactly the problem you are describing. If you need the functionality of an innodb, then should you first check the existence of the row, otherwise can you convert the table to a myisam table.
edit: if you need to check the existence of the row before the decision to insert or update, then would I advice you to use a stored procedure.
DELIMITER //
CREATE PROCEDURE adjustusers(IN pId int)
BEGIN
DECLARE userid int;
select count(id) into userid from users where id = pId;
if userid = 1 then
update users set id = pId where id = pId;
else
insert into users(id) values(pId);
end if;
END //
DELIMITER ;
A stored procedure is precompiled, just as a prepared statement. Hence no SQL injection problems and some more functionality and only one call to the database.

Complex INSERT query

I'm pretty new to MySQL. I have two related tables, quite common case: Klients(KID, name, surname) and Visits(VID, VKID, dateOfVisit) - VKID is the Klient ID. I have a problem with suitable INSERT query, this is what I want to do:
1.Check if Klient with specific name and surname exists (let's assume that there are no people with the same surnames)
2.If yes, get the ID and do the INSERT to Visits table
3.If no, INSERT new Klient, get the ID and INSERT to Visits.
Is it possible to do in one query?

You would need to use the IF EXIST / NOT EXISTS and use a subquery to check the table. See the reference bwlo
http://dev.mysql.com/doc/refman/5.0/en/exists-and-not-exists-subqueries.html
HTH

The INSERT statement allows only one single target table.
So the query you're looking for is just impossible unless you use triggers or stored procedures.
But such problem is commonly solved using the fallowing small algorithm:
1) insert a record in table [Visits] assuming the parent record does exist in table [Klients]
INSERT INTO Visits (VKID, dateOfVisit)
SELECT KID, NOW()
FROM Klients
WHERE (name=#name) AND (surname=#surname)
2) check the number of inserted records after query (1)
3) if no record has been inserted, then add a new record table [Klients], and then run (1) again.

try something like this
IF (SELECT * FROM `sometable` WHERE name = 'somename' AND surname = 'somesurname') IS NULL THEN
INSERT INTO Table1(name,surname) VALUES ('somename', 'somesurname');
ELSE INSERT INTO visits(kid,name,surname)
SELECT kid, name, surname FROM Table1 WHERE name = 'somename' AND surname = 'somesurname';
END IF;
there is no need to specify 'VALUES' on the second insert
i have not tested it, but this is the general idea of what you are trying to accomplish.

These should be two queries in a transaction:
INSERT INTO Klients (name, surname)
VALUES ('John', 'Doe')
ON DUPLICATE KEY UPDATE
KID = LAST_INSERT_ID(KID);
INSERT INTO Visits (VKID, dateOfVisits)
VALUES (LAST_INSERT_ID(), NOW());
The first statement is an upsert statement where the update part uses not widely known, but intented exactly for the purpose functionality of LAST_INSERT_ID(), where explicitly passed value is stored for getting the value afterwards.
UPD: I forgot to mention that you would need to add a unique constraint on (surname, name).

remove duplicate values while insertion

Hi I am trying to insert values from excel sheet into SQL Database in java. SQL database has already some rows inserted by some other techniques. Now I need to insert new rows from excel sheet and should eliminate the duplicate values which are existed in the database as well as in the excel sheet. For that I write a query like this.
First I inserted the records from excelsheet into SQL database by using insert query
Statement.executeUpdate(("INSERT INTO dbo.Company(CName,DateTimeCreated) values
('"+Cname”' ,'"+ts+"');
Later I deleted the duplicate values using delete query.
String comprows="delete from dbo.Company where Id not in"
+ "(select min(Id) from dbo.Company "
+ "group by CName having count(*)>=1)";
statement3.executeUpdate(comprows);
where Id is autoincremented integer.
but it is not good to do insert and then delete.
How do I know the values are already exist? If it is exist how do I remove during insertion???

You can simply fire a SELECT for the CName first. If a record is found, update else insert a new record.
Edited to add code snippet:
ResultSet rs = Statement.query("SELECT Id from dbo.Company where CNAME = '" +Cname + "'");
if(rs.next()) {
// retrieve ID from rs
// fire an update for this ID
} else {
// insert a new record.
}
Alternatively, if you think that there are already duplicates on your table and you want to remove them as well..
ResultSet rs = Statement.query("SELECT Id from dbo.Company where CNAME = '"+Cname + "'");
List idList = new ArrayList();
while(rs.next()) {
// collect IDs from rs in a collection say idList
}
if(!isList.isempty()) {
//convert the list to a comma seperated string say idsStr
Statement.executeUpdate("DELETE FROM dbo.Company where id in ("+ idsStr + ")");
}
// insert a new record.
Statement.executeUpdate(("INSERT INTO dbo.Company(CName,DateTimeCreated) values('"+Cname”' ,'"+ts+"');
Of course good practice is to use PreparedStatement as it would improve performance.
PS: Excuse me for any syntax errors.

One option would be to create a temp table and dump your Excel data there. Then you can write an insert that joins the temp table with the dbo.Company table and only insert the records that aren't already there.
You could do a lookup on each record you want to insert but if you are dealing with large volumes that's not a super efficient way to do it since you will have to do a select and an insert for each record in you excel spreadsheet.
Merge statements are pretty effective in these types of situations as well. I don't think all databases support them (I know Oracle does for sure). A merge statement is basically a combo insert and update so you can do the look up to the final table and insert if not found and update if found. The nice thing about this is you get the efficiency of doing all of this as a set rather than one record at a time.

If you can control the DB schema, you might consider putting a unique contraint for whatever column(s) to avoid duplicating. When you do your inserts, it'll throw when it tries to add the dup data. Catch it before it tosses you all the way out.
It's usually good to enforce constraints like this on the DB itself; that means no one querying the database has to worry about invalid duplicates. Also, optimistically trying the insert first (without doing a separate select first) might be faster.