Question 1: create a foreign key, couse_id, refer to table 2 to table 3 course_id create foreign keys
Refer to table 1 student_id, student_id create a foreign key for table 3
Question 2: retrieve the li qiang not learn course
Question 3: retrieve the courses that students of not less than 3 door student id
Question 4: retrieve not learn computer: "database principle" student
Question 5: give couse table couse_name create common indexes, how did he acquire indicating the length of the index
Question 6: to the course table student_id and course_id create joint index

CodePudding user response:

Although the questions are relatively simple, but the zha say is 6 issue, to 20 points, ah, ah...

CodePudding user response:

20 points really is too little, answer one spends a lot of time, forget it, I was passing by

CodePudding user response:

20 points, one I can answer it

CodePudding user response:

SQL statements are handwritten don't want to find other errors, a word is enough