sql查询语句之平均分、最高最低分及排序语句

目录

前言数据表数据查询各课程的考试学生人数查询各科成绩最高分和最低分查询男生、女生人数查询平均成绩查询平均成绩大于70分学生的学号和平均成绩查询学生考试参与考试课程数量查询考试两门以上课程的学生学号查询同名学生名单并统计同名人数计算每门课程的平均成绩计算每门课程的平均成绩并且平均成绩大于等于70分查询不及格的课程并按课程号从大到小排列查询每门课程的平均成绩，结果按平均成绩降序排列，如果平均成绩相同时，按课程号升序排列总结

前言

以mysql为例，汇总sql查询最高分、最低分、平均分等sql语句，oracle语法类似，可自行修改以下sql语句

创建两个数据库表，一个学生表、一个考试成绩表

DROP TABLE IF EXISTS `score`;

CREATE TABLE `score`  (

  `u_id` varchar(11) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT ‘编号’,

  `object_no` varchar(11) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT ‘课程编号’,

  `students_no` varchar(11) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT ‘学号’,

  `score` int(11) NULL DEFAULT NULL COMMENT ‘分数’

) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

INSERT INTO `score` VALUES (‘1’, ‘100’, ‘s100’, 80);

INSERT INTO `score` VALUES (‘2’, ‘100’, ‘s200’, 59);

INSERT INTO `score` VALUES (‘3’, ‘100’, ‘s300’, 79);

INSERT INTO `score` VALUES (‘4’, ‘200’, ‘s100’, 54);

INSERT INTO `score` VALUES (‘5’, ‘200’, ‘s200’, 96);

INSERT INTO `score` VALUES (‘6’, ‘200’, ‘s300’, 74);

INSERT INTO `score` VALUES (‘7’, ‘300’, ‘s100’, 65);

INSERT INTO `score` VALUES (‘8’, ‘300’, ‘s200’, 80);

INSERT INTO `score` VALUES (‘9’, ‘200’, ‘s400’, 62);

INSERT INTO `score` VALUES (’10’, ‘300’, ‘s400’, 56);

INSERT INTO `score` VALUES (’11’, ‘100’, ‘s400’, 70);

SET FOREIGN_KEY_CHECKS = 1;

DROP TABLE IF EXISTS `students`;

CREATE TABLE `students`  (

  `students_no` varchar(12) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT ‘编号’,

  `students_name` varchar(12) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT ‘姓名’,

  `sеx` varchar(1) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT ‘性别’,

  PRIMARY KEY (`students_no`) USING BTREE

) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

INSERT INTO `students` VALUES (‘s100’, ‘张三’, ‘1’);

INSERT INTO `students` VALUES (‘s200’, ‘李四’, ‘2’);

INSERT INTO `students` VALUES (‘s300’, ‘张三’, ‘1’);

INSERT INTO `students` VALUES (‘s400’, ‘王五’, ‘1’);

SET FOREIGN_KEY_CHECKS = 1;

数据表数据

查询各课程的考试学生人数

select object_no as ‘课程编号’, count(DISTINCT students_no) ‘考试人数’ from score group by object_no

查询各科成绩最高分和最低分

select object_no as ‘课程编号’,max(score) as ‘最高分’,min(score) as ‘最低分’ from score group by object_no

查询每门课程被选修的学生数

select object_no as ‘课程编号’, count(DISTINCT students_no) as ‘学生编号’ from score group by object_no

查询男生、女生人数

select sеx ‘性别’,count(DISTINCT students_no) ‘数量’ from students group by sеx

查询平均成绩

select students_no as ‘学生编号’,avg(score) as ‘平均成绩’ from score group by students_no

查询平均成绩大于70分学生的学号和平均成绩

select students_no as ‘学生编号’,avg(score) as ‘平均成绩’ from score group by students_no HАVING avg(score)>70

查询学生考试参与考试课程数量

select students_no as ‘学生编号’,count(object_no) as ‘课程编号’  from score   group by students_no

查询考试两门以上课程的学生学号

select students_no as ‘学生编号’,count(object_no) as ‘课程编号’  from score   group by students_no HАVING count( object_no)>2

查询同名学生名单并统计同名人数

select students_name as ‘学生名称’,count(students_name) as ‘同名数量’  from students group by students_name HАVING count(students_name)>1

计算每门课程的平均成绩

select object_no as ‘课程编号’,avg(score) as ‘平均成绩’ from score group by object_no

计算每门课程的平均成绩并且平均成绩大于等于70分

select object_no as ‘课程编号’,avg(score) as ‘平均成绩’ from score group by object_no HАVING avg(score)>70

查询不及格的课程并按课程号从大到小排列

select object_no as ‘课程编号’,students_no ‘学生编号’,score ‘分数’ from score where score<60 order by object_no desc

查询每门课程的平均成绩，结果按平均成绩降序排列，如果平均成绩相同时，按课程号升序排列

select object_no as ‘课程编号’,avg(score) as ‘平均成绩’ from score group by object_no order by avg(score) desc,object_no asc

总结

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