diff --git a/src/main/java/com/github/hcsp/sql/Sql.java b/src/main/java/com/github/hcsp/sql/Sql.java index c2bcf96..76e4d55 100644 --- a/src/main/java/com/github/hcsp/sql/Sql.java +++ b/src/main/java/com/github/hcsp/sql/Sql.java @@ -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 { @@ -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。 // +-----+ @@ -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： // +----+----------+------+----------+ @@ -100,7 +119,21 @@ 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; + 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 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 @@ -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 // +----+--------+------+ @@ -132,7 +169,21 @@ public String toString() { // | 3 | goods3 | 20 | // +----+--------+------+ public static List 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 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; + } } @@ -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： // +----------+-----------+------------+-------------+ @@ -170,12 +225,24 @@ public String toString() { // | 6 | zhangsan | goods3 | 20 | // +----------+-----------+------------+-------------+ public static List 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： // +----------+-----------+------------+-------------+ @@ -185,7 +252,7 @@ public static List getInnerJoinOrders(Connection databaseConnection) thro // +----------+-----------+------------+-------------+ // | 2 | lisi | goods1 | 10 | // +----------+-----------+------------+-------------+ -// | 3 | wangwu | goods1 | 20 | +// | 3 | lisi | goods1 | 20 | // +----------+-----------+------------+-------------+ // | 4 | zhangsan | goods2 | 80 | // +----------+-----------+------------+-------------+ @@ -198,10 +265,30 @@ public static List getInnerJoinOrders(Connection databaseConnection) thro // | 8 | NULL | NULL | 60 | // +----------+-----------+------------+-------------+ public static List 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 getJoinOrders(Connection databaseConnection, String sql) throws SQLException { + try (PreparedStatement statement = databaseConnection.prepareStatement(sql)) { + ResultSet resultSet = statement.executeQuery(); + List 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();