日考2

.gitignore

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+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### IntelliJ IDEA ###
+.idea
+*.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/$PROJECT_FILE$

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="AnalysisProjectProfileManager">
+    <option name="PROJECT_PROFILE" />
+    <option name="USE_PROJECT_LEVEL_SETTINGS" value="false" />
+    <list size="0" />
+  </component>
+  <component name="SuppressionsComponent">
+    <option name="suppComments" value="[]" />
+  </component>
+</project>

.idea/.gitignore

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

.idea/encodings.xml

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

.idea/inspectionProfiles/Project_Default.xml

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+<component name="InspectionProjectProfileManager">
+  <profile version="1.0">
+    <option name="myName" value="Project Default" />
+  </profile>
+</component>

.idea/misc.xml

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+<?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>
+  <component name="SuppressionsComponent">
+    <option name="suppComments" value="[]" />
+  </component>
+</project>

.idea/qaplug_profiles.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="AnalysisProjectProfileManager">
+    <option name="PROJECT_PROFILE" value="Project Default" />
+    <option name="USE_PROJECT_LEVEL_SETTINGS" value="false" />
+    <scopes />
+    <profiles>
+      <profile profile_name="Project Default" version="1.0" is_locked="false" />
+    </profiles>
+    <list size="0" />
+  </component>
+</project>

pom.xml

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+<?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>org.example</groupId>
+    <artifactId>rikao2</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/rikao2.sql

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+
+
+-- 3.查询男生和女生各多少人。（15分）
+SELECT sex,count(*) FROM t_student GROUP BY sex
+
+-- 4.	查询男生和女生分别占总人数的比例。（20分）
+SELECT sex,ROUND(count(*)/(SELECT count(*) FROM t_student),2) FROM t_student GROUP BY sex 
+
+-- 5.查询每门课程下的学生总人数。（15分）
+SELECT
+	c.c_name,count(*)
+FROM
+	t_student s
+	LEFT JOIN stu_cou sc on s.s_id = sc.s_id
+	LEFT JOIN t_course c on c.c_id = sc.c_id GROUP BY c.c_id
+	
+	
+	
+	
+CREATE TABLE `t_student`  (
+  `s_id` int NOT NULL AUTO_INCREMENT,
+  `s_name` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,
+  `sex` varchar(2) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,
+  PRIMARY KEY (`s_id`) USING BTREE
+) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_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', '男');
+INSERT INTO `t_student` VALUES (3, '王五', '男');
+INSERT INTO `t_student` VALUES (4, '赵六', '男');
+INSERT INTO `t_student` VALUES (5, '田七', '男');
+INSERT INTO `t_student` VALUES (6, '崔八', '男');
+INSERT INTO `t_student` VALUES (7, '春兰', '女');
+INSERT INTO `t_student` VALUES (8, '夏竹', '女');
+INSERT INTO `t_student` VALUES (9, '秋叶', '女');
+INSERT INTO `t_student` VALUES (10, '冬梅', '女');
+
+
+CREATE TABLE `t_course`  (
+  `c_id` int NOT NULL AUTO_INCREMENT,
+  `c_name` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,
+  PRIMARY KEY (`c_id`) USING BTREE
+) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = Dynamic;
+
+
+INSERT INTO `t_course` VALUES (1, '语文');
+INSERT INTO `t_course` VALUES (2, '数学');
+INSERT INTO `t_course` VALUES (3, '英语');
+
+
+
+CREATE TABLE `stu_cou`  (
+  `sc_id` int NOT NULL AUTO_INCREMENT,
+  `c_id` int NULL DEFAULT NULL,
+  `s_id` int NULL DEFAULT NULL,
+  PRIMARY KEY (`sc_id`) USING BTREE
+) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = Dynamic;
+
+
+INSERT INTO `stu_cou` VALUES (1, 1, 1);
+INSERT INTO `stu_cou` VALUES (2, 1, 2);
+INSERT INTO `stu_cou` VALUES (3, 1, 3);
+INSERT INTO `stu_cou` VALUES (4, 2, 4);
+INSERT INTO `stu_cou` VALUES (5, 2, 6);
+INSERT INTO `stu_cou` VALUES (6, 2, 5);
+INSERT INTO `stu_cou` VALUES (7, 3, 7);
+INSERT INTO `stu_cou` VALUES (8, 3, 8);
+INSERT INTO `stu_cou` VALUES (9, 3, 9);
+INSERT INTO `stu_cou` VALUES (10, 3, 10);
+
+	
+	

src/main/java/org/example/Main.java

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+package org.example;
+
+/**
+ * @Author：zhangzhihao
+ * @name：${NAME}
+ * @Date：2024/7/19 9:13
+ * 不准抄代码，添加注释，清楚每一行代码意思
+ */
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("Hello world!");
+    }
+}