Question

我正在使用以下数据库架构：

作者

Au_id
Au_lname
Au_fname
Phone
Address
City
State
Country
Postalcode

PUBLISHERS

Pub_id
Pub_name
City
State

TITLES

Title_id
Title, Type
Pub_id
Price
Advance
Total_sales
Notes
Pubdate
Contract

TITLEAUTHOR

Au_id
Title_id

店铺

Stor_id
Stor_name
Stor_address
City
State
Country
Postalcode
Payterms

销售

Stor_id
Ord_num
Sdate

SALESDETAIL

Stor_id
Ord_num
Title_id
Qty
Discount

我需要找到没有重复的Publisher Id和Publisher Name，他们已经在IS或IT上发布销量最高的书籍。

所以我写了这个查询：

SELECT DISTINCT PUBLISHERS.PUB_ID
    ,PUBLISHERS.PUB_NAME
FROM PUBLISHERS
INNER JOIN TITLES ON PUBLISHERS.PUB_ID = TITLES.PUB_ID
INNER JOIN SALESDETAIL ON TITLES.TITLE_ID = SALESDETAIL.TTITLE_ID
WHERE TITLES.TYPE = ‘IS’
    OR TITLES.TYPE = ‘IT’
    AND SALESDETAIL.QTY = MAX(SELECT COUNT(*) FROM SALESDETAIL GROUP BY TITLE_ID);

如果做得对，请帮助我吗？

Answer 1

如果你使用SQL Server，听起来你可以使用SELECT p.PUB_ID ,p.PUB_NAME ,max(sd.qty) OVER (PARTITION BY p.pub_id,p.pub_name ORDER BY p.pub_name) AS highest_sales FROM PUBLISHERS p INNER JOIN TITLES t ON p.PUB_ID = t.PUB_ID INNER JOIN SALESDETAIL sd ON t.TITLE_ID = sd.TITLE_ID WHERE (t.TYPE = 'IS' OR t.TYPE = 'IT');函数的窗口版本：

//generate your user data
User[] userData = ...;

//add an array of Objects to a JList using the constructor
//(all classes extend java.lang.Object, including User)
JList foo = new JList(userData);

//overwrite the ListCellRenderer. This will take care of just displaying
//the name of the user
foo.addListSelectionListener(new ListSelectionListener(){
    JLabel rv = new JLabel();
    @Override
    public Component getListCellRendererComponent(JList list,
            Object value, int index, boolean isSelected,
            boolean cellHasFocus){
        String s = (value != null && value instanceof User)? ((User)value).name:"";
        rv.setText(s);
        if (isSelected) {
            rv.setBackground(list.getSelectionBackground());
            rv.setForeground(list.getSelectionForeground());
        } else {
            rv.setBackground(list.getBackground());
            rv.setForeground(list.getForeground());
        }
        rv.setEnabled(list.isEnabled());
        rv.setFont(list.getFont());
        rv.setOpaque(true);
        return rv;
    }
});

//Now overwrite the ListSelectionListener which will take care of getting
//user object when the user clicks it
foo.addListSelectionListener(new ListSelectionListener(){
    @Override
    public void valueChanged(ListSelectionEvent lse) {
        User selectedValue = (User)((JList)lse.getSource()).getSelectedValue();
        //now you can do something with the User Object that was just selected
        updateDatabase(selectedValue.id, selectedValue.name,
                selectedValue.location);
});

查询以获取具有IS或IT Book类型的发布者

1 个答案: