Question

我编写了一个方法存根，到目前为止我在PreparedStatement中有这个SQL查询：

PreparedStatement ps = connection.prepareStatement("SELECT id,itemId,userId, sum(I.price) as totalAmount FROM dbo.Orders o 
join dbo.Items I on o.itemId = I.id join dbo.Users u on o.UserId = u.Id where o.id = ?");
            ps.setInt(1, id);

要求： 检索给定订单ID的不同项目值，并将它们添加到arrayList。

以下是我的方法到目前为止的样子：

    public ArrayList<Orders> GetOrders(Connection connection) throws Exception
            {
                ArrayList<Orders> feedData = new ArrayList<Orders>();
            ArrayList<Integer> itemsId = new ArrayList<Integer>();
//How do I get items in this arraylist since there could be multiple items for a given order ?
            try
        {
            PreparedStatement ps = connection.prepareStatement("SELECT id,itemId, userId, sum(I.price) as totalAmount FROM dbo.Orders o join dbo.Items I on o.itemId = I.id join dbo.Users u on o.UserId = u.Id where o.id = ? group by o.id");
            ps.setInt(1, id);
            ResultSet rs = ps.executeQuery();
            while(rs.next())
            {
                Orders o = new Orders();
                o.setId(rs.getInt("id"));
             //how do I add elements itemid's in itemsId array list here.?
                while(){

                }
                o.setItem(itemsId);
                o.setUserId(rs.getInt("price"));
                o.setTotalAmount(rs.getInt("totalAmount"));
                feedData.add(o);
            }
            return feedData;
        }
        catch(Exception e)
        {
            throw e;
        }
    }

编辑：

数据库架构：

create table Users
(
Id int not null primary Key identity(1,1) constraint fk_UserId_Id references Orders(UserId),
name nvarchar(50),
phone nvarchar(10)
);

create table Items
(
Id int not null primary Key identity(1,1) constraint fk_item_Id references Orders(ItemId),
name nvarchar(50),
Price int
);

create table Orders
(
id int not null primary Key identity(1,1),
ItemId int,
UserId int,
);

Answer 1

//这就是你要找的东西吗？

pushStore.getString("url")

Answer 2

基本上，您需要遍历所有返回的记录，即使您只想加载一个订单对象。

这是我所做的快速模拟，所以推迟批评，是的，它可以更好地实施。

public ArrayList<Orders> GetOrders( Connection connection ) throws Exception {
    ArrayList<Orders> feedData = new ArrayList<Orders>();
    int id = 0; // your Order ID
    try {
        PreparedStatement ps = connection.prepareStatement( "SELECT id,itemId, userId, sum(I.price) as totalAmount FROM dbo.Orders o join dbo.Items I on o.itemId = I.id join dbo.Users u on o.UserId = u.Id where o.id = ? group by o.id" );
        ps.setInt( 1, id );
        ResultSet rs = ps.executeQuery();

        ArrayList<Integer> itemsId = new ArrayList<Integer>();
        Orders o = new Orders();
        boolean populateOrder = true;

        while( rs.next() ) {

            itemsId.add( rs.getInt( "itemId" ) );

            if( populateOrder ) {
                o.setId( rs.getInt( "id" ) );
                o.setUserId( rs.getInt( "price" ) );
                o.setTotalAmount( rs.getInt( "totalAmount" ) );
                feedData.add( o );
                populateOrder = false; // make sure this If executes only once
            }
        }
        o.setItem( itemsId );

        return feedData;
    } catch( Exception e ) {
        throw e;
    }
}

以上示例有一个很大的限制，即它仅适用于单个订单（一个订单ID）。如果您希望加载多个代码需要更改的订单。

用于在arraylist中添加元素的SQL查询

2 个答案: