MySql single table query exercise

 

Students watch students

Table-building statement:  CREATE TABLE `students`  (   `name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '姓名',   `age` int (11) NULL DEFAULT NULL COMMENT 'age',   `gender` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT 'M=男, F=女' ) ENGINE = InnoDB CHARACTER SET = utf8; -Student table data: INSERT INTO `students` VALUES ('张 一', 12, 'Male'); INSERT INTO `students` VALUES ('Zhang Er', 18, 'Male'); INSERT INTO `students` VALUES ('Zhang Er', 19, 'Male'); INSERT INTO `students` VALUES ('Zhang San', 122, 'Male'); INSERT INTO `students` VALUES ('Zhang Si', 123, 'Male'); INSERT INTO `students` VALUES ('Zhang Wu', 161, 'Male'); INSERT INTO `students` VALUES ('Zhang Liu', 66, 'Male'); INSERT INTO `students` VALUES ('张 七', 35, 'Female'); INSERT INTO `students` VALUES ('Zhang Ba', 55, 'Male'); INSERT INTO `students` VALUES ('张 九', 56, 'Male'); INSERT INTO `students` VALUES ('张 十', 96, 'Male'); INSERT INTO `students` VALUES ('Zhang Eleven', 11, 'Male');

 

Single table basic query

1) Query all data in the table SELECT * FROM students 2) Display the NAME and age columns in the students table SELECT `name`,age FROM students; 3) The same name is displayed only once SELECT * FROM students GROUP BY `name` 4) The data in the query table is younger than 16 years old SELECT * FROM students WHERE age < 16 5) Query data older than 18 years old, and arrange them in reverse order SELECT * FROM students WHERE  age > 18 ORDER BY age DESC 6) Query the data between the ages of 18-30 (including 18, 30) SELECT * FROM students  WHERE  age BETWEEN 18 AND 30   # Query data between the ages of 18-30 (excluding 18, 30) SELECT * FROM students  WHERE  age >18  AND age <30 7) Query all data that is not 66 years old SELECT * FROM  students WHERE age !=66 8) Query the data of all names including "one" SELECT * FROM students WHERE `name` LIKE  '%一%'  9)统计表中男, 女的数量分别是多少 SELECT gender 性别,COUNT(*) 数量 FROM students  GROUP BY gender    10)查询表中所有数据平均年龄 SELECT  AVG(age) 平均年龄 FROM  students   11)查询最大年龄 SELECT MAX(age) FROM students   # 延伸 查询最大年龄的所有信息 SELECT  *  FROM students   WHERE   age=(SELECT MAX(age) FROM  students) # 查询最小年龄  SELECT MIN(age) FROM students

 

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