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Select sql #47

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e64094d
SELECT命令与JDBC使用
JiaXinWang61 Oct 31, 2019
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SELECT命令与JDBC使用
JiaXinWang61 Oct 31, 2019
2976d35
SELECT命令与JDBC使用
JiaXinWang61 Oct 31, 2019
8b7ff76
SELECT命令与JDBC使用
JiaXinWang61 Nov 1, 2019
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SELECT命令与JDBC使用
JiaXinWang61 Nov 10, 2019
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109 changes: 98 additions & 11 deletions src/main/java/com/github/hcsp/sql/Sql.java
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Original file line number Diff line number Diff line change
@@ -1,10 +1,14 @@

package com.github.hcsp.sql;

import java.io.File;
import java.math.BigDecimal;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.PreparedStatement;
import java.sql.DriverManager;
import java.util.ArrayList;
import java.util.List;

public class Sql {
Expand Down Expand Up @@ -72,8 +76,10 @@ 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
* @param databaseConnection 数据库连接
* @param goodsId 指定的商品ID
* @return 有多少用户买过这个商品
* @throws SQLException SQL异常
*/
// 例如，输入goodsId = 1，返回2，因为有2个用户曾经买过商品1。
// +-----+
Expand All @@ -82,16 +88,29 @@ public String toString() {
// | 2 |
// +-----+
public static int countUsersWhoHaveBoughtGoods(Connection databaseConnection, Integer goodsId) throws SQLException {
return 0;
try (PreparedStatement statement = databaseConnection.prepareStatement("select count(distinct USER_ID)\n" +
" 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
* @param databaseConnection 数据库连接
* @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
* @throws SQLException SQL异常
*/
// 例如，pageNum = 2, pageSize = 3（每页3个元素，取第二页），则应该返回：
// +----+----------+------+----------+
Expand All @@ -100,7 +119,21 @@ 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;
try (PreparedStatement statement = databaseConnection.prepareStatement("select * from USER order by id desc limit ?,?")) {
statement.setInt(1, pageSize);
statement.setInt(2, (pageNum - 1) * pageSize);
ResultSet resultSet = statement.executeQuery();
List<User> users = 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);
users.add(user);
}
return users;
}
}

// 商品及其营收
Expand All @@ -118,6 +151,10 @@ 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
*
* @param databaseConnection 数据库连接
* @return 所有的商品及其销售额，按照销售额从大到小排序
* @throws SQLException SQL异常
*/
// 预期的结果应该如图所示
// +----+--------+------+
Expand All @@ -132,7 +169,21 @@ public String toString() {
// | 3 | goods3 | 20 |
// +----+--------+------+
public static List<GoodsAndGmv> getGoodsAndGmv(Connection databaseConnection) throws SQLException {
return null;
try (PreparedStatement statement = databaseConnection.prepareStatement("select \"ORDER\".GOODS_ID as ID, GOODS.NAME, " +
"sum(GOODS_NUM * GOODS_PRICE) as GMV\n" +
"from \"ORDER\"\n" +
" join GOODS on \"ORDER\".GOODS_ID = GOODS.ID group by \"ORDER\".GOODS_ID order by GMV desc")) {
ResultSet resultSet = statement.executeQuery();
List<GoodsAndGmv> goodsAndGmvs = new ArrayList<>();
while (resultSet.next()) {
GoodsAndGmv goodsAndGmv = new GoodsAndGmv();
goodsAndGmv.goodsId = resultSet.getInt(1);
goodsAndGmv.goodsName = resultSet.getString(2);
goodsAndGmv.gmv = resultSet.getBigDecimal(3);
goodsAndGmvs.add(goodsAndGmv);
}
return goodsAndGmvs;
}
}


Expand All @@ -152,6 +203,10 @@ 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
*
* @param databaseConnection 数据库连接
* @return 查询订单信息，只查询用户名、商品名齐全的订单
* @throws SQLException SQL异常
*/
// 预期的结果为：
// +----------+-----------+------------+-------------+
Expand All @@ -170,12 +225,24 @@ public String toString() {
// | 6 | zhangsan | goods3 | 20 |
// +----------+-----------+------------+-------------+
public static List<Order> getInnerJoinOrders(Connection databaseConnection) throws SQLException {
return null;
String sql = "select \"ORDER\".USER_ID as order_id,\n" +
" USER.NAME as user_name,\n" +
" GOODS.NAME as goods_name,\n" +
" (\"ORDER\".GOODS_NUM * \"ORDER\".GOODS_PRICE) as total_price\n" +
"from \"ORDER\"\n" +
" join GOODS on \"ORDER\".GOODS_ID = GOODS.ID\n" +
" join USER on \"ORDER\".USER_ID = USER.ID";
return getJoinOrders(databaseConnection, sql);

}

/**
* 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
*
* @param databaseConnection 数据库连接
* @return 查询所有订单信息，哪怕它的用户名、商品名缺失
* @throws SQLException SQL异常
*/
// 预期的结果为：
// +----------+-----------+------------+-------------+
Expand All @@ -185,7 +252,7 @@ public static List<Order> getInnerJoinOrders(Connection databaseConnection) thro
// +----------+-----------+------------+-------------+
// | 2 | lisi | goods1 | 10 |
// +----------+-----------+------------+-------------+
// | 3 | wangwu | goods1 | 20 |
// | 3 | lisi | goods1 | 20 |
// +----------+-----------+------------+-------------+
// | 4 | zhangsan | goods2 | 80 |
// +----------+-----------+------------+-------------+
Expand All @@ -198,10 +265,30 @@ public static List<Order> getInnerJoinOrders(Connection databaseConnection) thro
// | 8 | NULL | NULL | 60 |
// +----------+-----------+------------+-------------+
public static List<Order> getLeftJoinOrders(Connection databaseConnection) throws SQLException {
return null;
String sql = "select \"ORDER\".USER_ID as Order_id, USER.NAME as user_name, GOODS.NAME as goods_name, (\"ORDER\".GOODS_NUM * \"ORDER\".GOODS_PRICE) as total_price\n" +
"from \"ORDER\"\n" +
" left join GOODS on \"ORDER\".GOODS_ID = goods.id\n" +
" left join USER on \"ORDER\".USER_ID = USER.ID";
return getJoinOrders(databaseConnection, sql);
}

// 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 List<Order> getJoinOrders(Connection databaseConnection, String sql) throws SQLException {
try (PreparedStatement statement = databaseConnection.prepareStatement(sql)) {
ResultSet resultSet = statement.executeQuery();
List<Order> orders = 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);
orders.add(order);
}
return orders;
}
}

public static void main(String[] args) throws SQLException {
File projectDir = new File(System.getProperty("basedir", System.getProperty("user.dir")));
String jdbcUrl = "jdbc:h2:file:" + new File(projectDir, "target/test").getAbsolutePath();
Expand Down