diff --git a/src/main/java/com/github/hcsp/sql/Sql.java b/src/main/java/com/github/hcsp/sql/Sql.java index 418a0df..7425375 100644 --- a/src/main/java/com/github/hcsp/sql/Sql.java +++ b/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 { @@ -57,7 +56,9 @@ public class Sql { // 用户信息 public static class User { - Integer id; + + public static Integer id; + String name; String tel; String address; @@ -74,7 +75,9 @@ public String toString() { * * @param goodsId 指定的商品ID * @return 有多少用户买过这个商品 + * @param databaseConnection */ + // 例如，输入goodsId = 1，返回2，因为有2个用户曾经买过商品1。 // +-----+ // |count| @@ -82,16 +85,26 @@ public String toString() { // | 2 | // +-----+ public static int countUsersWhoHaveBoughtGoods(Connection databaseConnection, Integer goodsId) throws SQLException { + 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 0; + + } /** * 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 + * @param databaseConnection */ // 例如，pageNum = 2, pageSize = 3（每页3个元素，取第二页），则应该返回： // +----+----------+------+----------+ @@ -100,25 +113,45 @@ public static int countUsersWhoHaveBoughtGoods(Connection databaseConnection, In // | 1 | zhangsan | tel1 | beijing | // +----+----------+------+----------+ public static List getUsersByPageOrderedByIdDesc(Connection databaseConnection, int pageNum, int pageSize) throws SQLException { - return null; - } + List users = new ArrayList<>(); + try (PreparedStatement statement = databaseConnection.prepareStatement("select * from user order by id desc limit (?-1)*?,?")) { + statement.setInt(1, pageNum); + statement.setInt(2, pageSize); + statement.setInt(3, pageSize); + ResultSet resultSet = statement.executeQuery(); + users = new ArrayList<>(); + while (resultSet.next()) { + User user = new User(); + user.id = resultSet.getInt(1); + user.name = resultSet.getNString(2); + user.tel = resultSet.getString(3); + user.address = resultSet.getNString(4); - // 商品及其营收 - public static class GoodsAndGmv { - Integer goodsId; // 商品ID - String goodsName; // 商品名 - BigDecimal gmv; // 商品的所有销售额 + users.add(user); + } + } + return users; - @Override - public String toString() { - return "GoodsAndGmv{" + "goodsId=" + goodsId + ", goodsName='" + goodsName + '\'' + ", gmv=" + gmv + '}'; } - } - /** - * 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 - */ + // 商品及其营收 + public static class GoodsAndGmv { + Integer goodsId; // 商品ID + String goodsName; // 商品名 + BigDecimal gmv; // 商品的所有销售额 + + @Override + public String toString() { + return "GoodsAndGmv{" + "goodsId=" + goodsId + ", goodsName='" + goodsName + '\'' + ", gmv=" + gmv + '}'; + } + } + + /** + * 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 + * @return tag + */ // 预期的结果应该如图所示 // +----+--------+------+ // | ID | NAME | GMV | @@ -131,28 +164,47 @@ public String toString() { // +----+--------+------+ // | 3 | goods3 | 20 | // +----+--------+------+ - public static List getGoodsAndGmv(Connection databaseConnection) throws SQLException { - return null; - } + public static List getGoodsAndGmv (Connection databaseConnection) throws SQLException { + List gmvList = new ArrayList<>(); + try (PreparedStatement statement = databaseConnection.prepareStatement("select `order`.goods_id, goods.name, `order`.goods_price * sum(`order`.goods_num) as gmv from `order`\n" + + "join goods\n" + + "on `order`.goods_id = goods.id\n" + + "group by `order`.goods_id\n" + + "order by gmv desc")) { + ResultSet resultSet = statement.executeQuery(); + while (resultSet.next()) { + GoodsAndGmv goodsAndGmv = new GoodsAndGmv(); + goodsAndGmv.goodsId = resultSet.getInt(1); + goodsAndGmv.goodsName = resultSet.getString(2); + goodsAndGmv.gmv = resultSet.getBigDecimal(3); + gmvList.add(goodsAndGmv); + } + } + return gmvList; - // 订单详细信息 - public static class Order { - Integer id; // 订单ID - String userName; // 用户名 - String goodsName; // 商品名 - BigDecimal totalPrice; // 订单总金额 + } - @Override - public String toString() { - return "Order{" + "id=" + id + ", userName='" + userName + '\'' + ", goodsName='" + goodsName + '\'' + ", totalPrice=" + totalPrice + '}'; + + // 订单详细信息 + public static class Order { + Integer id; // 订单ID + String userName; // 用户名 + String goodsName; // 商品名 + BigDecimal totalPrice; // 订单总金额 + + @Override + public String toString() { + return "Order{" + "id=" + id + ", userName='" + userName + '\'' + ", goodsName='" + goodsName + '\'' + ", totalPrice=" + totalPrice + '}'; + } } - } - /** - * 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 - */ + /** + * 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 + * @return tag + */ // 预期的结果为： // +----------+-----------+------------+-------------+ // | ORDER_ID | USER_NAME | GOODS_NAME | TOTAL_PRICE | @@ -169,14 +221,35 @@ public String toString() { // +----------+-----------+------------+-------------+ // | 6 | zhangsan | goods3 | 20 | // +----------+-----------+------------+-------------+ - public static List getInnerJoinOrders(Connection databaseConnection) throws SQLException { - return null; - } + public static List getInnerJoinOrders (Connection databaseConnection) throws SQLException { + List orders = new ArrayList<>(); - /** - * 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 - */ + try (PreparedStatement statement = databaseConnection.prepareStatement("select `order`.id as order_id, user.name as user_name, goods.name as goods_name, `order`.goods_price * sum(`order`.goods_num) as total_price from `order`\n" + + "join goods\n" + + "\ton `order`.goods_id = goods.id\n" + + "join user\n" + + "\ton `order`.user_id = user.id\n" + + "group by `order`.id")) { + ResultSet resultSet = statement.executeQuery(); + 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; + + } + + /** + * 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 + * @return tag + * @param databaseConnection + */ // 预期的结果为： // +----------+-----------+------------+-------------+ // | ORDER_ID | USER_NAME | GOODS_NAME | TOTAL_PRICE | @@ -197,21 +270,51 @@ public static List getInnerJoinOrders(Connection databaseConnection) thro // +----------+-----------+------------+-------------+ // | 8 | NULL | NULL | 60 | // +----------+-----------+------------+-------------+ - public static List getLeftJoinOrders(Connection databaseConnection) throws SQLException { - return null; - } + public static List getLeftJoinOrders (Connection databaseConnection) throws SQLException { + List orders = new ArrayList<>(); - // 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"))); - String jdbcUrl = "jdbc:h2:file:" + new File(projectDir, "target/test").getAbsolutePath(); - try (Connection connection = DriverManager.getConnection(jdbcUrl, "root", "Jxi1Oxc92qSj")) { - System.out.println(countUsersWhoHaveBoughtGoods(connection, 1)); - System.out.println(getUsersByPageOrderedByIdDesc(connection, 2, 3)); - System.out.println(getGoodsAndGmv(connection)); - System.out.println(getInnerJoinOrders(connection)); - System.out.println(getLeftJoinOrders(connection)); + try (PreparedStatement statement = databaseConnection.prepareStatement("select `order`.id AS ORDER_ID, \n" + + "\t\tuser.name AS USER_NAME, \n" + + "\t\tgoods.name AS GOODS_NAME, \n" + + "\t\t`order`.goods_price * sum(`order`.goods_num) AS total_price \n" + + "from `order`\n" + + "\tleft join goods\n" + + "\t\ton `order`.goods_id = goods.id\n" + + "\tleft join user\n" + + "\t\ton `order`.user_id = user.id\n" + + "group by `order`.id")) { + ResultSet resultSet = statement.executeQuery(); + 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; + + + } + // 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"))); + String jdbcUrl = "jdbc:h2:file:" + new File(projectDir, "target/test").getAbsolutePath(); + try (Connection connection = DriverManager.getConnection(jdbcUrl, "root", "Jxi1Oxc92qSj")) { + System.out.println(Sql.countUsersWhoHaveBoughtGoods(connection, 1)); + System.out.println(Sql.getUsersByPageOrderedByIdDesc(connection, 2, 3)); + System.out.println(Sql.getGoodsAndGmv(connection)); + System.out.println(getInnerJoinOrders(connection)); + System.out.println(getLeftJoinOrders(connection)); + } } } -} + + + + + + +