diff --git a/src/main/java/com/github/hcsp/sql/Sql.java b/src/main/java/com/github/hcsp/sql/Sql.java
index 418a0df..c5c4c88 100644
--- a/src/main/java/com/github/hcsp/sql/Sql.java
+++ b/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 {
@@ -68,39 +68,47 @@ public String toString() {
         }
     }
 
-    /**
-     * 题目1：
-     * 查询有多少所有用户曾经买过指定的商品
-     *
-     * @param goodsId 指定的商品ID
-     * @return 有多少用户买过这个商品
-     */
-// 例如，输入goodsId = 1，返回2，因为有2个用户曾经买过商品1。
+
 // +-----+
 // |count|
 // +-----+
 // | 2   |
 // +-----+
     public static int countUsersWhoHaveBoughtGoods(Connection databaseConnection, Integer goodsId) throws SQLException {
-        return 0;
+        try (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 pageSize 每页有多少个元素
-     * @return 指定页中的用户
-     */
-// 例如，pageNum = 2, pageSize = 3（每页3个元素，取第二页），则应该返回：
+
 // +----+----------+------+----------+
 // | ID | NAME     | TEL  | ADDRESS  |
 // +----+----------+------+----------+
 // | 1  | zhangsan | tel1 | beijing  |
 // +----+----------+------+----------+
     public static List<User> getUsersByPageOrderedByIdDesc(Connection databaseConnection, int pageNum, int pageSize) throws SQLException {
-        return null;
+        try (PreparedStatement statement = databaseConnection.prepareStatement("select id, name, tel ,address from `user`  ORDER BY ID DESC limit ?,?")) {
+            statement.setInt(1, pageSize * (pageNum - 1));
+            statement.setInt(2, pageSize);
+            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
@@ -115,11 +123,7 @@ public String toString() {
         }
     }
 
-    /**
-     * 题目3：
-     * 查询所有的商品及其销售额，按照销售额从大到小排序
-     */
-// 预期的结果应该如图所示
+
 //  +----+--------+------+
 //  | ID | NAME   | GMV  |
 //  +----+--------+------+
@@ -132,7 +136,19 @@ public String toString() {
 //  | 3  | goods3 | 20   |
 //  +----+--------+------+
     public static List<GoodsAndGmv> getGoodsAndGmv(Connection databaseConnection) throws SQLException {
-        return null;
+        try (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;
+        }
     }
 
 
@@ -149,11 +165,7 @@ public String toString() {
         }
     }
 
-    /**
-     * 题目4：
-     * 查询订单信息，只查询用户名、商品名齐全的订单，即INNER JOIN方式
-     */
-// 预期的结果为：
+
 // +----------+-----------+------------+-------------+
 // | ORDER_ID | USER_NAME | GOODS_NAME | TOTAL_PRICE |
 // +----------+-----------+------------+-------------+
@@ -170,14 +182,22 @@ public String toString() {
 // | 6        | zhangsan  | goods3     | 20          |
 // +----------+-----------+------------+-------------+
     public static List<Order> getInnerJoinOrders(Connection databaseConnection) throws SQLException {
-        return null;
+        try (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;
+        }
     }
 
-    /**
-     * 题目5：
-     * 查询所有订单信息，哪怕它的用户名、商品名缺失，即LEFT JOIN方式
-     */
-// 预期的结果为：
 // +----------+-----------+------------+-------------+
 // | ORDER_ID | USER_NAME | GOODS_NAME | TOTAL_PRICE |
 // +----------+-----------+------------+-------------+
@@ -198,7 +218,19 @@ public static List<Order> getInnerJoinOrders(Connection databaseConnection) thro
 // | 8        | NULL      | NULL       | 60          |
 // +----------+-----------+------------+-------------+
     public static List<Order> getLeftJoinOrders(Connection databaseConnection) throws SQLException {
-        return null;
+        try (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