3 there is a table, specific information fields as follows:
Student table (exam_t_student): Student id (student_id),
Student Name (student_name),
Class id (class_id),
Sex (gender)
Class table (exam_t_class): class id (class_id),
Grade (level)
Results table (exam_t_class): No. (grade_id),
Student id (student_id),
Subject (subject),
Achievement (grade)
Complete the following sql
1. Please provide each class of third-grade score average (output column: class id, average boys and girls average, class average)
2. Please provide the proportion of students in each grade in Zhang's (output columns: Year id, accounting)
3. Please provide each grade in language examinations highest score (output columns: grades, scores)
4. Please provide the number of classes in school more than 30 people and the number is greater than the number of boys and girls in the class list (asking for a trial having, output column: grade, class)
5. Please provide each school subjects more than 90 points in the student's name (output column: grade, name)
6. Please provide a year before out of a list ranking 10 (output column: student's name, score, rank)
7. Please provide a subject grade math scores ranking (output column: student's name, score, class rank, grade ranking)
The answer in the next issue