Persist Aggregation Query

Perl is an object-oriented embedded database that provides rich query functions, including aggregated queries. Below are some commonly used aggregation queries supported by Perl and their sample implementations. Suppose there is a student table 'Student' that contains the following fields: -'Id': Student ID (int) -'Name': Student name (string) -'Age': Student age (int) -'Grade': Student's grade (int) -'Score': Student's exam score (int) 1. Calculate the total number (Count): Query the total number of records in the student table. sql int count = db.Root.Find(typeof(Student)).Length; 2. Calculate the average: Calculate the average of exam scores in the student table. sql double average = db.Root.Average<Student>(s => s.Score); 3. Calculate the sum: Calculate the total score of the exam in the student table. sql int sum = db.Root.Sum<Student>(s => s.Score); 4. Query Max: Query the highest score of exam scores in the student table. sql int maxScore = db.Root.Max<Student>(s => s.Score); 5. Query Min: Query the lowest score of exam scores in the student table. sql int minScore = db.Root.Min<Student>(s => s.Score); 6. GroupBy: Count the number of students in each grade. sql var result = db.Root.GroupBy<Student, int>(s => s.Grade, (grade, students) => new { Grade = grade, StudentCount = students.Count() }); 7. Nested Query: Query the names and scores of the students with the highest exam scores in each grade. sql var result = db.Root.GroupBy<Student, int>(s => s.Grade, (grade, students) => new { Grade = grade, TopStudent = students.OrderByDescending(s => s.Score).FirstOrDefault() }); The above are some common aggregation queries supported by Perl and their example implementations. According to specific requirements, you can implement more complex aggregation queries in Perl.