practise-select-sql

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

@@ -2,9 +2,8 @@
 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 {
@@ -82,7 +81,15 @@ public String toString() {
 // | 2   |
 // +-----+
     public static int countUsersWhoHaveBoughtGoods(Connection databaseConnection, Integer goodsId) throws SQLException {
-        return 0;
+       try (PreparedStatement preparedStatement = databaseConnection.prepareStatement("select count(distinct user_id) from \"ORDER\" where goods_id = ? ")) {
+            preparedStatement.setInt(1, goodsId);
+            try (ResultSet resultSet = preparedStatement.executeQuery()) {
+                while (resultSet.next()) {
+                    return resultSet.getInt(1);
+                }
+            }
+            return -1;
+        }
     }
 
     /**
@@ -100,7 +107,25 @@ 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;
+       try (PreparedStatement preparedStatement = databaseConnection.prepareStatement("select * from user order by id desc limit(?-1)*?,?")) {
+            preparedStatement.setInt(1, pageNum);
+            preparedStatement.setInt(2, pageSize);
+            preparedStatement.setInt(3, pageSize);
+
+            List<User> list;
+            try (ResultSet resultSet = preparedStatement.executeQuery()) {
+                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 +157,23 @@ public String toString() {
 //  | 3  | goods3 | 20   |
 //  +----+--------+------+
     public static List<GoodsAndGmv> getGoodsAndGmv(Connection databaseConnection) throws SQLException {
-        return null;
+       try (PreparedStatement preparedStatement = databaseConnection.prepareStatement("select goods.id as id,name,sum(goods_num*goods_price) as gmv from goods\n" +
+                "join `order`\n" +
+                "on goods.id = `order`.goods_id\n" +
+                "group by goods.id\n" +
+                "order by gmv desc")) {
+            List<GoodsAndGmv> list = new ArrayList<>();
+            try (ResultSet resultSet = preparedStatement.executeQuery()) {
+                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 +211,24 @@ public String toString() {
 // | 6        | zhangsan  | goods3     | 20          |
 // +----------+-----------+------------+-------------+
     public static List<Order> getInnerJoinOrders(Connection databaseConnection) throws SQLException {
-        return null;
+        try (PreparedStatement preparedStatement = databaseConnection.prepareStatement("select `order`.id,user.name,goods.name,goods_price * goods_num as total_price from `order`\n" +
+                "join goods\n" +
+                "on goods.id = `order`.goods_id\n" +
+                "join user\n" +
+                "on user.id = `order`.user_id")) {
+            try (ResultSet resultSet = preparedStatement.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;
+            }
+        }
     }
 
     /**
@@ -198,9 +256,27 @@ 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 preparedStatement = databaseConnection.prepareStatement("select `order`.id,user.name,goods.name,goods_price * goods_num as total_price from `order`\n" +
+                "left join  goods\n" +
+                "on goods.id = `order`.goods_id\n" +
+                "left join  user\n" +
+                "on user.id = `order`.user_id")) {
+            try (ResultSet resultSet = preparedStatement.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
     public static void main(String[] args) throws SQLException {
         File projectDir = new File(System.getProperty("basedir", System.getProperty("user.dir")));