I'm new to java and I need help with displaying a joined table/query in jtable.
First, I have done displaying data from 1 table which is:
Select data from 1 table
insert the result to its entity and insert each one of it to a List
return the list to view and insert row to jtable
I am using a DAO pattern, which has a factory, interface, implement, entity and view.
So what if I select data from other table?
Here is my get method in implement for getting book
public List get(String find) {
try {
ps = db.connect().prepareStatement("SELECT * FROM books WHERE title like ? ");
ps.setString(1, "%" + find + "%");
status = db.execute(ps);
if (status) {
books = db.get_result();
listBooks = new ArrayList<>();
while (books.next()) {
entity_books b = new entity_books();
b.setId(books.getInt(1));
b.setId_category(books.getInt(2));
b.setTitle(books.getString(3));
listBooks.add(b);
}
books.close();
return listBooks;
}
} catch (SQLException e) {
System.out.println(e.getMessage());
}
return null;
}
and then in my view:
listBooks = booksDAO.get(find.getText());
model = (DefaultTableModel) book_table.getModel();
model.setRowCount(0);
listBooks.forEach((data) -> {
model.addRow(new Object[]{
data.getId(),
data.getId_category(),
data.getTitle(),
});
});
This works fine, but I want the query to join table so I can see the category name instead of just ID category. I can do the query, but how do I apply that to my code?
Here is the query for joined table
select title,category from book b
join category c on c.id = b.id_category
Normally if I select only 1 table, I would insert it to its entity ( book table -> book entity ), so how do I handle this with multiple tables?
I didn't use prepared statement, but this code works on my end.
String sql = "SELECT * FROM customer c JOIN company cmp ON c.company_idcompany = cmp.idcompany";
ResultSet rs = stmt.executeQuery(sql);
//STEP 5: Extract data from result set
while (rs.next()) {
//Retrieve this from customer table
int id = rs.getInt("idcustomer");
//Retrieve this from customer table
String username = rs.getString("company_username");
//Display values
System.out.println("ID: " + id);
System.out.println("Username: " + username);
}
Related
Requirement : I have a file from which I need to add the assistant employee id corresponding to it's manager into db. So in file I am getting login id of assistant. I need to pass the login id to db in order to fetch the corresponding employee id of the assistant and add into the list which I am getting from file.
// code for getting employee from file - returns a list
private void setAssistantEmployeeId(List<E> empFile){
List<E> empFilter = empFile.stream().filter(emp -> emp.getLoginId()!=null).collect(Collectors.toList());
String sql = "SELECT ID FROM EMPLOYEE WHERE LOGIN_ID = ";
List<E> tempList = new ArrayList<>(empFilter);
for(E emp : empFilter){
tempList.addAll(jdbcTemplate.query(sql+emp.getLoginId(), (resultset,i)->{
emp.setAssistantEmployeeId(resultset.getString("ID"));
return emp;
}));
}
}
The above code is working as expected but it's taking lot of time to execute. I need some help to optimize this code. Can someone please help me in optimizing this code?
Thank you.
private void setAssistantEmployeeId(List<E> empFile) throws SQLException {
List<E> empFilter = empFile.stream().filter(emp -> emp.getLoginId()!=null).collect(Collectors.toList());
//1. query all LOGIN_ID
String sql = "SELECT ID, LOGIN_ID FROM EMPLOYEE WHERE LOGIN_ID IN (" + empFilter.stream().map(emp -> emp.getLoginId())
.collect(Collectors.joining("','")) + ")";
// create map[LOGIN_ID, ID]
ResultSet rs = runQuery(sql); // execute this query in your way
Map<String, String> id_loginId = new HashMap<>();
while (rs.next()) {
id_loginId.put(rs.getString("LOGIN_ID"), rs.getString("ID"));
}
// 3. assign ID value
empFilter.forEach(e -> {
e.setAssistantEmployeeId(id_loginId.getOrDefault(e.getLoginId(), ""));
});
}
There are three tables <Table 1>, <Table 2> and <Table 3>
My SQL is something like this:
"Select table1.col1, table1.col2, table1.col3, table2.col4, table2.col5, table2.col6,
table3.col7, table3.col8 from Table 1 as table1
LEFT JOIN Table 2 as table2 on (table1.col1 = table2.col4)
LEFT JOIN Table 3 as table3 on (table1.col1 = table3.col8)"
The normal way to get the resultset is:
public List getExportDataList() throws ClassNotFoundException, SQLException {
Connection connect = null;
String url = "jdbc:.....";
String username = "username ";
String password = "password ";
try {
connect = DriverManager.getConnection(url, username, password);
} catch (SQLException ex) {
System.out.println("in exec");
System.out.println(ex.getMessage());
}
List dataList = new ArrayList<>();
PreparedStatement pstmt = connect.prepareStatement(
THE SQL CODE SHOWN ABOVE
}
ResultSet rs = pstmt.executeQuery();
while(rs.next()){
Table1 table1 = new Table1();
table1.setCOL1(rs.getString("col1"));
table1.setCOL2(rs.getString("col2"));
dataList.add(table1);
}
rs.close();
pstmt.close();
connect.close();
return dataList;
}
so that the "dataList" can be used to display the data in Primefaces dataTable.
However, this way only can save the columns in Table1 to the "dataList". I tried to dataList.add(table2) as well as dataList.add(table3) at the same time, but there is an error : "/reportGenerate.xhtml #50,75 value="#{reportData.dateCreated}": The class 'net.picary.model.Liaison' does not have the property 'dateCreated'."
Can someone tell me how to save all the selected columns from the three tables into "dataList"? Or any alternative way to achieve it?
error: "/reportGenerate.xhtml #50,75
value="#{reportData.dateCreated}": The class
'net.picary.model.Liaison' does not have the property 'dateCreated'."
Your problem is not with Query or JDBC, you should to make sure that attribute dateCreated exist in your net.picary.model.Liaison class with getter and setter like this :
private Date dateCreated;
public String name;
public String experience;
public Date getDateCreated() {
return dateCreated;
}
public void setDateCreated(Date dateCreated) {
this.dateCreated = dateCreated;
}
So when your page reportGenerate.xhtml try to load this attribute it not find it, because :
Not exist in your class
It exist but it is private and without getter and setter.
So make sure that your attribute exist and have gtter and setter, this can solve your error.
EDIT
You have two choices :
When you get your result you should to use 3 List of type table1, table2, table3 and fill them in the same loop like this :
List dataList1 = ...;
List dataList2 = ...;
List dataList3 = ...;
while(rs.next()){
table1 = new Table1();
table1.setCOL1(rs.getString("col1"));
...
dataList1.add(table1);
table2 = new Table2();
table2.setCOL1(rs.getString("col1"));
...
dataList2.add(table2);
table3 = new Table3();
table3.setCOL1(rs.getString("col1"));
...
dataList3.add(table3);
}
and in your xhtml page you had to use this three List instead to one
Create a new Object which combine this three Table like this :
class MyObject {
private Table1 table1;
private Table2 table2;
//constructor
//getters and setters
}
Then create a List<MyObject> list = ....; and set information in each table.
Hope you get my point, good luck
First, Check whether column names (col1,col2,col3,..) are with same name in your code in java with all the three db tables (table1,table2,table3).
(ie)
...
Table1 table1 = new Table1();
table1.setCOL1(rs.getString("col1"));
table1.setCOL2(rs.getString("col2"));
dataList.add(table1);
....
In the above code check you have "col1" is in same name with db column in Table1,Table2,Table3.If the column name(s) is different in database and in your code ,add aliases to your MySQL query and match it with same name in your java code.
If the column name matches, then set the column value for your table 2 and 3.
Then, add it to your Datalist.
....
....
table2.setCOL1(rs.getString("col1"));
dataList.add(table2);
....
and so on. Also, check you have added try/catch for your code to avoid exceptions like Nullpointer,SQLException etc.. which may arise during SQL transactions.
I have 3 tables having the following content :
Author
idAuthor INT
name VARCHAR
Publication
idPublication INT
Title VARCHAR
Date YEAR
Type VARCHAR
Conference
author_has_publication
author_idAuthor INT
publication_idPublication INT
I am trying to do relational schema on the authors. The objectif is to show the number of publication they have in common. The authors name are parameters, I can have up to 8 names. My code is giving the number of common publication between 2 authors, so i have to loop it. I am currently using a Java loop and SQL statement to do that. Here is the SQL part
private int runQuery(String a1, String a2){ // a1 author 1 and a2 author 2
try {
auth1 = new ArrayList<String>();
Class.forName("com.mysql.jdbc.Driver");
Connection connection = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/mydb", "root", "ROOT");
Statement stmt = connection.createStatement();
long start = System.currentTimeMillis();
String queryUpdate1 = "DROP TABLE IF EXISTS temp1;";
String queryUpdate2 = "DROP TABLE IF EXISTS temp2;";
String queryUpdate3 = "CREATE TEMPORARY TABLE IF NOT EXISTS temp1 AS (SELECT Author.name, Publication.idPublication, Publication.title FROM Author INNER JOIN Author_has_Publication ON Author_has_Publication.author_idAuthor=author.idAuthor INNER JOIN Publication ON Author_has_Publication.publication_idPublication=publication.idPublication WHERE Author.name='"+ a1+"');";
String queryUpdate4 = "CREATE TEMPORARY TABLE IF NOT EXISTS temp2 AS (SELECT Author.name, Publication.idPublication, Publication.title FROM Author INNER JOIN Author_has_Publication ON Author_has_Publication.author_idAuthor=author.idAuthor INNER JOIN Publication ON Author_has_Publication.publication_idPublication=publication.idPublication WHERE Author.name='"+ a2+"');";
String query = "SELECT COUNT(*) FROM (SELECT temp1.title from temp1 INNER JOIN temp2 on temp1.idPublication = temp2.idPublication) as t;";
stmt.executeUpdate(queryUpdate1);
stmt.executeUpdate(queryUpdate2);
stmt.executeUpdate(queryUpdate3);
stmt.executeUpdate(queryUpdate4);
ResultSet rs = stmt.executeQuery(query);
int result = -1;
while (rs.next()) {
result = rs.getInt(1);
}
System.out.println("result = " + result);
long end = System.currentTimeMillis() - start;
queryTimeLabel.setText("Query Execution Time :"+end);
connection.close();
return result;
} catch (Exception e) {
System.out.println(e);
}
return -1;
}
Here is the loop part (to repeat the SQL when there are more than 2 authors given) and generate the graph :
public void actionPerformed(ActionEvent e) {
graph = new mxGraph();
Object parent = graph.getDefaultParent();
authVertex = getAuthors();
// ///////////////////////////////////
// CREATES GRAPH, Graph only shows up after you resize the window
graph.getModel().beginUpdate();
try {
int i = 0;
for(String a: authVertex.keySet()){
int j = 0;
for(String b: authVertex.keySet()){
if(j > i) {
graph.insertEdge(parent, null, String.valueOf(runQuery(a,b)), authVertex.get(a), authVertex.get(b)); // loop the SQL statement 2 by 2.
}
j++;
}
i++;
}
} finally {
graph.getModel().endUpdate();
}
graphComponent = new mxGraphComponent(graph);
graphPan.removeAll();
graphPan.add(graphComponent);
setVisible(true);
// /////////////////////////////////////////
}
My code is currently working, but I would like to know if it was possible to increase the performance by passing everything into MySQL, that means that I enter the authors name in parameter and the loop is hangled by MySQL, I check the MySQL procedure but my issue is how to handle the authors names parameter as it is a variable.
One way, in a single statement:
SELECT COUNT(*)
FROM Author_has_Publication AS ap1
JOIN Author_has_Publication AS ap2 ON ap1.publication_idPublication =
ap2.publication_idPublication
JOIN Author AS a1 ON ap1.author_idAuthor = a1.id_Author
JOIN Author AS a2 ON ap2.author_idAuthor = a2.id_Author
WHERE a1.name = '...'
AND a2.name = '...'
Another way may be
SELECT COUNT(*)
FROM
(
SELECT ahp.publication_idPublication, COUNT(*)
FROM Author_has_Publication AS ahp
JOIN Author AS a ON a.id_Author = ahp.author_idAuthor
WHERE a.name IN ('...', '...')
GROUP BY ahp.publication_idPublication
HAVING COUNT(*) = 2 -- Number of authors
) x
Composite indexes needed:
Author_has_Publication: (author_idAuthor, publication_idPublication)
Author_has_Publication: (publication_idPublication, author_idAuthor)
Author: (name, id)
Note: Each technique can be rather easily extended to more than 2 authors. The second query could even be adapted to "at least 3 of these 5 authors": 5 names in IN and HAVING COUNT(*) >= 3.
I have a sqlite database in android , for example :
Table 1 person:
column 1: id
column 2: name
column 3: friends
Table 2 friends:
column 1: id
column 2: allFriends
the id is the same in both tables, id in table1 == id in table2
i want to get all the values from table2 in specific column "allFriends" by the id and insert all the String values from the column into String array / arrayList.
Try this,
public ArrayList<String> getAllFriends(int id) {
ArrayList<String> friendsNames = new ArrayList<>();
SQLiteDatabase sqLiteDatabase = null;
try {
String query = "select * from person P join friends F on F.id = P.id where P.id = " + id;
Cursor cursor = sqLiteDatabase.rawQuery(query, null);
while (cursor.moveToNext()) {
friendsNames.add(cursor.getString(cursor.getColumnIndex("allFriends")));
}
}catch(Exception ex){
Log.e(TAG,"Erro in geting friends "+ex.toString());
}
return friendsNames;
}
Your SQL query:
SELECT allFriends FROM friends where id == Id_from_person
Id_from_person - id of person who friends you want to recieve from DB.
For executing query read this.
I have 2 database tables for my program: GameInfo and Characters.
How this works is that a Game has 4 maps with different names and each character added to the game must be assigned any of the 4 maps. Now I have the sql statement which returns a result set named "Expr1001, of the number of characters on each map. I then need to add this information to a jTable and link up the corresponding amount of each characterson a map, with the mapname.
My ResultSet with the query which returns the amount of characters on each map:
ResultSet qs = dbm.queryDatabase("SELECT Expr1001 FROM (SELECT GameInfo.mapname, SUM(IIF(Map = GameInfo.mapname,1,0)) FROM (SELECT * FROM [Character] INNER JOIN Player ON Character.PlayerID=Player.[ID]) AS A RIGHT JOIN GameInfo ON A.Character.map = GameInfo.mapname GROUP BY GameInfo.mapname) AS [%$###_Alias]");
The whole method which gets the Game Info from the database from the GameInfo table, which comprises of a GameID and MapName only.
public Game[] getGameInfo(){
Game[] arr = null; //Creates an array of Games
try { //getting list from database
ResultSet rs = dbm.queryDatabase("Select Count(GameID) as NumGames from GameInfo" );
//While there are still more rows to read from the database.
rs.next();
int count = rs.getInt("NumGames");
arr = new Game[count];
String sql = "Select * from GameInfo";
// System.out.println(sql);
rs = dbm.queryDatabase(sql);
//Take the info from the current row
//Add the info to the array
ResultSet qs = dbm.queryDatabase("SELECT Expr1001 FROM (SELECT GameInfo.mapname, SUM(IIF(Map = GameInfo.mapname,1,0)) FROM (SELECT * FROM [Character] INNER JOIN Player ON Character.PlayerID=Player.[ID]) AS A RIGHT JOIN GameInfo ON A.Character.map = GameInfo.mapname GROUP BY GameInfo.mapname) AS [%$###_Alias]");
for(int i = 0; rs.next(); i++){
arr[i] = new Game(
rs.getInt("GameInfo.GameID"),
rs.getString("GameInfo.mapname"),
qs.getInt(i));
}//Creates a Game from the currently selected info
} catch (Exception e) {
JOptionPane.showMessageDialog(null, "Failed to get Games");
e.printStackTrace();
}
return arr;
}
}
The data is then added to the jTable which is on a Panel in the GameInfoPanel class:
public void refreshTable() {
//remove old stuff
refreshing = true;
Game[] arr = gim.getGameInfo();
DefaultTableModel model = (DefaultTableModel) GameInfoTable.getModel();
while (model.getRowCount() > 0) {
model.removeRow(0);
}
for (int i = 0; i < arr.length; i++) {
model.addRow(new Object[]{
arr[i].getNumberOfCharacters(),
arr[i].getID(),
arr[i].getMapName()});
}
refreshing = false;
//load new data from database using manager
}
I keep getting the error which points to the ResultSet qs line: "user lacks privilege or object not found: A.CHARACTER.MAP" when I try and run the program even though when I copy this statement into Microsoft Access and run it, it's fine.
Help please!
Thanks.
(I am still at school so not really a genius on this at all so please have mercy if I've done some stupid things)
Don't run a select count(*) first to get the number of games for allocating an array. Build you result in a List, which will auto-expand as needed. You can always convert the list to an array later, if needed.
Don't run two queries when one can do the job, especially when you already join to the table in question.
Your SQL is unreadable, so here it is in a more readable format:
String sql = "SELECT Expr1001" +
" FROM (SELECT GameInfo.mapname" +
", SUM(IIF(Map = GameInfo.mapname,1,0))" +
" FROM (SELECT *" +
" FROM [Character]" +
" INNER JOIN Player ON Character.PlayerID=Player.[ID]" +
") AS A" +
" RIGHT JOIN GameInfo ON A.Character.map = GameInfo.mapname" +
" GROUP BY GameInfo.mapname" +
") AS [%$###_Alias]";
The outer query does nothing. Get rid of it.
Don't SELECT *. Select the columns you want, i.e. Character.map.
Since you want GameID, add it to the GROUP BY.
Specify an alias for the SUM value.
public Game[] getGameInfo(){
String sql = " SELECT GameInfo.GameID" +
", GameInfo.mapname" +
", SUM(IIF(C.map = GameInfo.mapname,1,0)) AS CharacterCount" +
" FROM ( SELECT Character.map" +
" FROM [Character]" +
" JOIN Player ON Player.[ID] = Character.PlayerID" +
") C" +
" RIGHT JOIN GameInfo ON GameInfo.mapname = C.map" +
" GROUP BY GameInfo.GameID" +
", GameInfo.mapname";
try (ResultSet rs = dbm.queryDatabase(sql)) {
List<Game> games = new ArrayList<>();
while (rs.next())
games.add(new Game(rs.getInt("GameID"),
rs.getString("mapname"),
rs.getInt("CharacterCount")));
return games.toArray(new Game[games.size()]);
} catch (Exception e) {
JOptionPane.showMessageDialog(null, "Failed to get Games");
e.printStackTrace();
return null;
}
}