SELECT命令与JDBC使用

src/main/java/com/github/hcsp/sql/Sql.java

@@ -1,10 +1,10 @@
 
 package com.github.hcsp.sql;
+
 import java.io.File;
 import java.math.BigDecimal;
-import java.sql.Connection;
-import java.sql.DriverManager;
-import java.sql.SQLException;
+import java.sql.*;
+import java.util.ArrayList;
 import java.util.List;
 
 public class Sql {
@@ -82,14 +82,20 @@ public String toString() {
 // | 2   |
 // +-----+
     public static int countUsersWhoHaveBoughtGoods(Connection databaseConnection, Integer goodsId) throws SQLException {
-        return 0;
+        PreparedStatement statement = databaseConnection.prepareStatement("select count(distinct user_id) from `order` where goods_id = ?");
+        statement.setInt(1, goodsId);
+        ResultSet resultSet = statement.executeQuery();
+        while (resultSet.next()) {
+            return resultSet.getInt(1);
+        }
+        return -1;
     }
 
     /**
      * 题目2：
      * 分页查询所有用户，按照ID倒序排列
      *
-     * @param pageNum 第几页，从1开始
+     * @param pageNum  第几页，从1开始
      * @param pageSize 每页有多少个元素
      * @return 指定页中的用户
      */
@@ -100,7 +106,21 @@ public static int countUsersWhoHaveBoughtGoods(Connection databaseConnection, In
 // | 1  | zhangsan | tel1 | beijing  |
 // +----+----------+------+----------+
     public static List<User> getUsersByPageOrderedByIdDesc(Connection databaseConnection, int pageNum, int pageSize) throws SQLException {
-        return null;
+        PreparedStatement statement = databaseConnection.prepareStatement("select id, name, tel ,address from `user`  ORDER BY ID DESC limit ?,?");
+        statement.setInt(1, pageSize * (pageNum - 1));//2 2,2
+        statement.setInt(2, pageSize);//2
+        ResultSet resultSet = statement.executeQuery();
+
+        List<User> list = new ArrayList<>();
+        while (resultSet.next()) {
+            User user = new User();
+            user.id = resultSet.getInt(1);
+            user.name = resultSet.getString(2);
+            user.tel = resultSet.getString(3);
+            user.address = resultSet.getString(4);
+            list.add(user);
+        }
+        return list;
     }
 
     // 商品及其营收
@@ -132,7 +152,17 @@ public String toString() {
 //  | 3  | goods3 | 20   |
 //  +----+--------+------+
     public static List<GoodsAndGmv> getGoodsAndGmv(Connection databaseConnection) throws SQLException {
-        return null;
+        PreparedStatement statement = databaseConnection.prepareStatement("select goods_id ,name,sum(goods_num * goods_price) as GMV from `order` join goods on `order`.goods_id = goods.id group by goods_id order by GMV desc");
+        ResultSet resultSet = statement.executeQuery();
+        List<GoodsAndGmv> list = new ArrayList<>();
+        while (resultSet.next()) {
+            GoodsAndGmv goodsAndGmv = new GoodsAndGmv();
+            goodsAndGmv.goodsId = resultSet.getInt(1);
+            goodsAndGmv.goodsName = resultSet.getString(2);
+            goodsAndGmv.gmv = resultSet.getBigDecimal(3);
+            list.add(goodsAndGmv);
+        }
+        return list;
     }
 
 
@@ -170,7 +200,18 @@ public String toString() {
 // | 6        | zhangsan  | goods3     | 20          |
 // +----------+-----------+------------+-------------+
     public static List<Order> getInnerJoinOrders(Connection databaseConnection) throws SQLException {
-        return null;
+        PreparedStatement statement = databaseConnection.prepareStatement("select `order`.id, user.name, goods.name,goods_price*goods_num as total from `order` join user on `order`.user_id = user.id join goods on `order`.goods_id = goods.id");
+        ResultSet resultSet = statement.executeQuery();
+        List<Order> list = new ArrayList<>();
+        while (resultSet.next()) {
+            Order order = new Order();
+            order.id = resultSet.getInt(1);
+            order.userName = resultSet.getString(2);
+            order.goodsName = resultSet.getString(3);
+            order.totalPrice = resultSet.getBigDecimal(4);
+            list.add(order);
+        }
+        return list;
     }
 
     /**
@@ -198,7 +239,18 @@ public static List<Order> getInnerJoinOrders(Connection databaseConnection) thro
 // | 8        | NULL      | NULL       | 60          |
 // +----------+-----------+------------+-------------+
     public static List<Order> getLeftJoinOrders(Connection databaseConnection) throws SQLException {
-        return null;
+        PreparedStatement statement = databaseConnection.prepareStatement("select `order`.id, user.name, goods.name,goods_price*goods_num as total from `order` left join user on `order`.user_id = user.id left join goods on `order`.goods_id = goods.id");
+        ResultSet resultSet = statement.executeQuery();
+        List<Order> list = new ArrayList<>();
+        while (resultSet.next()) {
+            Order order = new Order();
+            order.id = resultSet.getInt(1);
+            order.userName = resultSet.getString(2);
+            order.goodsName = resultSet.getString(3);
+            order.totalPrice = resultSet.getBigDecimal(4);
+            list.add(order);
+        }
+        return list;
     }
 
     // 注意，运行这个方法之前，请先运行mvn initialize把测试数据灌入数据库