test02

.gitignore

@@ -0,0 +1,38 @@
+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store

.idea/.gitignore

@@ -0,0 +1,8 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml

.idea/encodings.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="Encoding">
+    <file url="file://$PROJECT_DIR$/src/main/java" charset="UTF-8" />
+    <file url="file://$PROJECT_DIR$/src/main/resources" charset="UTF-8" />
+  </component>
+</project>

.idea/misc.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ExternalStorageConfigurationManager" enabled="true" />
+  <component name="MavenProjectsManager">
+    <option name="originalFiles">
+      <list>
+        <option value="$PROJECT_DIR$/pom.xml" />
+      </list>
+    </option>
+  </component>
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" default="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
+</project>

pom.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.bwie</groupId>
+    <artifactId>test02</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>

sql/test002.sql

@@ -0,0 +1,117 @@
+/*
+ Navicat Premium Data Transfer
+
+ Source Server         : lyx
+ Source Server Type    : MySQL
+ Source Server Version : 50736
+ Source Host           : 111.229.181.183:3306
+ Source Schema         : test002
+
+ Target Server Type    : MySQL
+ Target Server Version : 50736
+ File Encoding         : 65001
+
+ Date: 19/07/2024 09:07:53
+*/
+
+SET NAMES utf8mb4;
+SET FOREIGN_KEY_CHECKS = 0;
+
+-- ----------------------------
+-- Table structure for stu_cou
+-- ----------------------------
+DROP TABLE IF EXISTS `stu_cou`;
+CREATE TABLE `stu_cou`  (
+  `sc_id` int(11) NOT NULL AUTO_INCREMENT,
+  `c_id` int(11) NULL DEFAULT NULL,
+  `s_id` int(11) NULL DEFAULT NULL,
+  PRIMARY KEY (`sc_id`) USING BTREE
+) ENGINE = InnoDB AUTO_INCREMENT = 14 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;
+
+-- ----------------------------
+-- Records of stu_cou
+-- ----------------------------
+INSERT INTO `stu_cou` VALUES (1, 1, 1);
+INSERT INTO `stu_cou` VALUES (2, 1, 2);
+INSERT INTO `stu_cou` VALUES (3, 1, 5);
+INSERT INTO `stu_cou` VALUES (4, 2, 3);
+INSERT INTO `stu_cou` VALUES (5, 2, 4);
+INSERT INTO `stu_cou` VALUES (6, 2, 7);
+INSERT INTO `stu_cou` VALUES (7, 2, 9);
+INSERT INTO `stu_cou` VALUES (8, 3, 10);
+INSERT INTO `stu_cou` VALUES (9, 3, 6);
+INSERT INTO `stu_cou` VALUES (10, 3, 8);
+INSERT INTO `stu_cou` VALUES (11, 2, 8);
+INSERT INTO `stu_cou` VALUES (12, 1, 10);
+INSERT INTO `stu_cou` VALUES (13, 3, 2);
+
+-- ----------------------------
+-- Table structure for t_course
+-- ----------------------------
+DROP TABLE IF EXISTS `t_course`;
+CREATE TABLE `t_course`  (
+  `c_id` int(11) NOT NULL AUTO_INCREMENT,
+  `c_name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
+  PRIMARY KEY (`c_id`) USING BTREE
+) ENGINE = InnoDB AUTO_INCREMENT = 7 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;
+
+-- ----------------------------
+-- Records of t_course
+-- ----------------------------
+INSERT INTO `t_course` VALUES (1, '英语');
+INSERT INTO `t_course` VALUES (2, '语文');
+INSERT INTO `t_course` VALUES (3, '数学');
+
+-- ----------------------------
+-- Table structure for t_student
+-- ----------------------------
+DROP TABLE IF EXISTS `t_student`;
+CREATE TABLE `t_student`  (
+  `s_id` int(11) NOT NULL AUTO_INCREMENT,
+  `s_name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
+  `sex` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
+  PRIMARY KEY (`s_id`) USING BTREE
+) ENGINE = InnoDB AUTO_INCREMENT = 21 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;
+
+-- ----------------------------
+-- Records of t_student
+-- ----------------------------
+INSERT INTO `t_student` VALUES (1, '张三', '男');
+INSERT INTO `t_student` VALUES (2, '李四', '女');
+INSERT INTO `t_student` VALUES (3, '王五', '男');
+INSERT INTO `t_student` VALUES (4, '赵六', '女');
+INSERT INTO `t_student` VALUES (5, '田七', '男');
+INSERT INTO `t_student` VALUES (6, '晓丽', '女');
+INSERT INTO `t_student` VALUES (7, '关谷', '男');
+INSERT INTO `t_student` VALUES (8, '架子', '男');
+INSERT INTO `t_student` VALUES (9, '淞沪', '女');
+INSERT INTO `t_student` VALUES (10, '威威', '女');
+
+SET FOREIGN_KEY_CHECKS = 1;
+
+
+-- 查询男生人数
+SELECT COUNT(*) AS count
+FROM t_student
+WHERE sex = '男';
+
+-- 查询女生人数
+SELECT COUNT(*) AS n_count
+FROM t_student
+WHERE sex = '女';
+
+-- 查询男生占比
+SELECT COUNT(*) * 100.0 / (SELECT COUNT(*) FROM t_student) AS people_nan
+FROM t_student
+WHERE sex = '男';
+
+-- 查询女生占比
+SELECT COUNT(*) * 100.0 / (SELECT COUNT(*) FROM t_student) AS people_nv
+FROM t_student
+WHERE sex = '女';
+
+-- 查询每门课程下的学生总人数
+SELECT c.c_name AS course_name, COUNT(sc.s_id) AS student_count
+FROM t_course c
+       LEFT JOIN stu_cou sc ON c.c_id = sc.c_id
+GROUP BY c.c_name