我需要连接两个表，
表1
public class CreateScheme extends Application {
// Variablen
ContextMenu contextMenu = new ContextMenu();
MenuItem item1 = new MenuItem("Tooltip erstellen");
private Model model;
private Pane root;
TableView<Model> tableview = new TableView<Model>();
VBox vbox3 = new VBox();
private Tooltip tooltip = new Tooltip();
TableCell<Model, String> cell = new TableCell<>();
@Override
public void start(Stage secondStage) throws Exception {
// Scene / root
root = new Pane(); // Layout -> alle Elmente haben die Position 0/0
Scene scene = new Scene(root, 800, 600);
// Variablen erstellen
VBox vbox = new VBox();
VBox vbox2 = new VBox();
HBox hbox = new HBox();
HBox hbox2 = new HBox();
HBox hbox3 = new HBox();
Label label = new Label("Bewertungsschema erstellen: ");
Button button = new Button("New");
TextField textField1 = new TextField();
CheckBox checkbox = new CheckBox();
Button addButton = new Button("Erstellen");
Button cancelButton = new Button("Abbrechen");
Button saveButton = new Button("Speichern");
Button addTextFieldButton = new Button("+");
Button bold = new Button("F");
Button redButton = new Button("Fehler markieren");
ObservableList<Model> list = FXCollections.observableArrayList();
model = new Model();
model.addListener(e -> {
while (e.next()) {
if (e.wasAdded()) {
int ix = model.size() - 1; // fängt bei Überschrift Table 1 an.
for (Model m : list) {
if (m.size() <= ix) {
m.add("");
}
}
TableColumn<Model, String> column = new TableColumn<Model, String>("Table" + (ix + 1));
column.setCellFactory(TextFieldTableCell.<Model>forTableColumn());
column.setCellValueFactory(feature -> feature.getValue().get(ix));
column.setEditable(true);
tableview.getColumns().add(column);
}
}
});
cell.getStyleClass().add("cellmy");
tableview.setItems(list);
tableview.setEditable(true);
textField1.setVisible(false);
checkbox.setVisible(false);
vbox2.setVisible(false);
hbox.setSpacing(10.0);
hbox.getChildren().addAll(button, textField1, checkbox);
vbox.setLayoutX(10.0);
vbox.setLayoutY(30.0);
vbox.setSpacing(30.0);
vbox.setPadding(new Insets(10.0, 20.0, 30.0, 10.0));
vbox.getChildren().addAll(label, hbox, redButton, bold);
vbox2.setLayoutX(300.0);
vbox2.setLayoutY(30.0);
vbox2.setSpacing(30.0);
vbox2.setMaxHeight(200.0);
vbox2.setPadding(new Insets(50.0, 30.0, 30.0, 30.0));
vbox2.getChildren().add(tableview);
hbox2.setLayoutX(10.0);
hbox2.setLayoutY(500.0);
hbox2.setSpacing(20.0);
hbox3.setLayoutX(10.0);
hbox3.setLayoutY(550.0);
hbox3.setSpacing(20.0);
hbox3.getChildren().addAll(addButton, cancelButton, saveButton, addTextFieldButton);
contextMenu.getItems().addAll(item1);
button.setOnAction(new EventHandler<ActionEvent>() {
public void handle(ActionEvent e) {
textField1.setVisible(true);
checkbox.setVisible(true);
}
});
checkbox.setOnAction(new EventHandler<ActionEvent>() {
public void handle(ActionEvent e) {
vbox2.setVisible(true);
textField1.setEditable(false);
}
});
addTextFieldButton.setOnAction(event -> {
TextField textfield = new TextField();
int ix = model.size();
model.add("");
textfield.textProperty().bindBidirectional(model.get(ix));
hbox2.getChildren().add(textfield);
});
addButton.setOnAction(new EventHandler<ActionEvent>() {
public void handle(ActionEvent e) {
// list.add(new Model());
tableview.refresh();
}
});
addButton.setOnAction(new EventHandler<ActionEvent>() {
public void handle(ActionEvent e) {
model.addTo(list);
model.reset();
}
});
saveButton.setOnAction(new EventHandler<ActionEvent>() {
public void handle(ActionEvent e) {
FileChooser fileChooser = new FileChooser();
// Set extension filter
FileChooser.ExtensionFilter extFilter = new FileChooser.ExtensionFilter("TXT files (*.txt)", "*.txt");
fileChooser.getExtensionFilters().add(extFilter);
// Show save file dialog
File file = fileChooser.showSaveDialog(secondStage);
if (file != null) {
saveTextToFile(root, file);
}
}
});
tableview.setTooltip(tooltip);
item1.setOnAction(new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent event) {
showInputTextDialog();
}
});
tableview.setOnContextMenuRequested(new EventHandler<ContextMenuEvent>() {
@Override
public void handle(ContextMenuEvent event) {
contextMenu.show(tableview, event.getScreenX(), event.getScreenY());
}
});
root.getChildren().addAll(vbox, vbox2, hbox2, hbox3);
scene.getStylesheets().add("style.css");
secondStage.setTitle("Bewertungsschema erstellen");
secondStage.setScene(scene);
secondStage.show();
}
private void showInputTextDialog() {
TextInputDialog dialog = new TextInputDialog("Tran");
dialog.setTitle("Bemerkung");
dialog.setHeaderText("Meine Notiz:");
dialog.setContentText("Bemerkung:");
Optional<String> result = dialog.showAndWait();
result.ifPresent(name -> {
this.tooltip.setText(name);
});
if (result != null) {
tableview.setStyle("-fx-background-color: red;");
}
}
private void saveTextToFile(Pane pane2, File file) {
try {
PrintWriter writer;
writer = new PrintWriter(file);
writer.println(pane2);
writer.close();
} catch (IOException ex) {
Logger.getLogger(CreateScheme.class.getName()).log(Level.SEVERE, null, ex);
}
}
public Pane getPane2() {
return this.root;
}
public static void main(String[] args) {
launch(args);
}
}
public class Model {
private final ObservableList<SimpleStringProperty> properties = FXCollections.observableArrayList();
public void addListener(ListChangeListener<? super SimpleStringProperty> listener) {
properties.addListener(listener);
}
public void add(String value) {
properties.add(new SimpleStringProperty(value));
}
public int size() {
return properties.size();
}
public Property<String> get(int ix) {
return properties.get(ix);
}
public void addTo(List<Model> list) {
Model copy = new Model();
for (SimpleStringProperty prop : properties) {
copy.add(prop.getValue());
}
list.add(copy);
}
public void reset() {
for (SimpleStringProperty prop : properties) {
prop.setValue("");
}
}
}
表2
t1_id | t1_text | t1_date
我想要得到什么：
t2_id | t2_text | t2_date | t1_id
表必须显示最新的唯一t1行及其链接的t2_text及其t2_date
这是我到目前为止所得到的：
t1_text | t1_date | t2_text | t2_date
它很近，但是没有雪茄。我仍然得到相同的t1行以多次显示
答案 0 :(得分：0)
关于id字段的唯一性的说明：
select t1.t1_id, t1.t1_date, t1.t1_text, t2.t2_id, t2.t2_date, t2.t2_text
from table_1 t1
inner join (SELECT t1_id, max(t1_date) as date from table_1) t1m
on t1.t1_id = t1m.t1_id and t1.t1_date = t1m.date
inner join table_2 t2
on t1.t1_id = t2.t1_id
inner join (SELECT t2_id, max(t2_date) as date from table_2) t2m
on t2.t2_id = t2m.t2_id and t2.t2_date = t2m.date;
在此查询中，内联表选择具有最大日期的ID，然后将其与原始表结合以获取其余字段。
如果t1_id和t1_date的组合不是唯一的，仍然可能有重复的t1_id。但是在那种情况下，我不认为应该隐藏重复项，而应该解决它。
原始答案：
您需要使用内部联接，而不是左联接。
SELECT `table_1`.`t1_text` AS 'Text', `table_1`.`t1_date` AS 't1_date', `table_2`.`t2_text` AS 't2_Text', `table_2`.`t2_date` AS 'Date'
FROM `table_1`
INNER JOIN `table_2`
ON `table_1`.`t1_id`=`table_2`.`t1_id`
ORDER BY `table_1`.`t1_date` DESC LIMIT 10
此外，您的某些引号字符不一致，不同的数据库可能需要使用不同的引号字符来分隔名称，但混合使用可能会给您带来麻烦。
答案 1 :(得分：0)
我不确定我是否清楚理解您想要的输出是什么。请尝试以下操作：
SELECT news.text AS 'News', news.date AS 'Publish date',
comments.text AS 'Most Recent Comment', comments.date AS 'Comment Date'
FROM news
JOIN (
SELECT text, MAX(newsId) as newsId, date
FROM comments
GROUP BY newsId
)comments ON news.newsId=comments.newsId
WHERE comments.text IS NOT NULL
ORDER BY news.date DESC LIMIT 10