日考二文件

.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

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>com.bwie</groupId>
+    <artifactId>test_day2</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>17</maven.compiler.source>
+        <maven.compiler.target>17</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>

sql/test_6_2.sql

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+/*
+ Navicat Premium Data Transfer
+
+ Source Server         : 106.54.199.209
+ Source Server Type    : MySQL
+ Source Server Version : 80400
+ Source Host           : 106.54.199.209:3306
+ Source Schema         : test_6_2
+
+ Target Server Type    : MySQL
+ Target Server Version : 80400
+ File Encoding         : 65001
+
+ Date: 19/07/2024 09:05:01
+*/
+
+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 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;
+
+-- ----------------------------
+-- 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, 3);
+INSERT INTO `stu_cou` VALUES (4, 1, 4);
+INSERT INTO `stu_cou` VALUES (5, 2, 5);
+INSERT INTO `stu_cou` VALUES (6, 2, 6);
+INSERT INTO `stu_cou` VALUES (7, 2, 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);
+INSERT INTO `stu_cou` VALUES (11, 3, 11);
+INSERT INTO `stu_cou` VALUES (12, 3, 2);
+
+-- ----------------------------
+-- Table structure for t_course
+-- ----------------------------
+DROP TABLE IF EXISTS `t_course`;
+CREATE TABLE `t_course`  (
+  `c_id` int NOT NULL AUTO_INCREMENT,
+  `c_name` varchar(255) 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;
+
+-- ----------------------------
+-- Records of t_course
+-- ----------------------------
+INSERT INTO `t_course` VALUES (1, '云计算');
+INSERT INTO `t_course` VALUES (2, '大数据');
+INSERT INTO `t_course` VALUES (3, '全栈');
+
+-- ----------------------------
+-- Table structure for t_student
+-- ----------------------------
+DROP TABLE IF EXISTS `t_student`;
+CREATE TABLE `t_student`  (
+  `s_id` int NOT NULL AUTO_INCREMENT,
+  `s_name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,
+  `sex` varchar(255) 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', '女');
+INSERT INTO `t_student` VALUES (5, '陈琴', '女');
+INSERT INTO `t_student` VALUES (6, '杨洋', '男');
+INSERT INTO `t_student` VALUES (7, '刘八', '女');
+INSERT INTO `t_student` VALUES (8, '小红', '女');
+INSERT INTO `t_student` VALUES (9, '小宝', '男');
+INSERT INTO `t_student` VALUES (10, '小柳', '女');
+INSERT INTO `t_student` VALUES (11, '老七', '男');
+
+SET FOREIGN_KEY_CHECKS = 1;

sql/日考二sql语句.sql

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+--  查询男生和女生各多少人
+-- 男生
+SELECT COUNT(t_student.s_id) FROM t_student WHERE t_student.sex = '男'
+
+-- 女生
+SELECT COUNT(t_student.s_id) FROM t_student WHERE t_student.sex = '女'
+
+
+--	查询男生和女生分别占总人数的比例
+
+
+
+  SELECT     (SELECT COUNT(t_student.s_id) FROM t_student WHERE t_student.sex = '男')  / (SELECT COUNT(t_student.s_id) FROM t_student) * 100 
+
+ SELECT     (SELECT COUNT(t_student.s_id) FROM t_student WHERE t_student.sex = '女')  / (SELECT COUNT(t_student.s_id) FROM t_student) * 100 
+
+
+-- 查询每门课程下的学生总人数。
+
+SELECT
+	t_course.c_name,
+	COUNT( t_student.s_id ) 
+FROM
+	t_course
+	LEFT JOIN stu_cou ON t_course.c_id = stu_cou.c_id
+	LEFT JOIN t_student ON t_student.s_id = stu_cou.s_id
+	
+	GROUP BY t_course.c_id