I am studying SQL in my data science degree program, and the assignment is to perform SQL queries for the first time. In order to do that, I have to paste the SQL starter code in and run it. However, when I do, I hit an error that I can’t solve. My class is online and my professor hasn’t responded and, since this isn’t part of the graded part of the assignment, I figured I’d try here to get help on this error.
Edit: It was pointed out that I didn’t include all of the tables. Please see full code for all tables and all data. I was trying to avoid flooding this post with a lot of lines of code, but it seems I left out pertinent information. See below.
The tables were created with these blocks of code:
create table section ( course_id varchar(8), sec_id varchar(8), semester varchar(6) check (semester in ('Fall', 'Winter', 'Spring', 'Summer')), year numeric(4,0) check (year >1701 and year < 2100), building varchar(15), room_number varchar(7), time_slot_id varchar(4), primary key (course_id, sec_id, semester, year), foreign key (course_id) references course on delete cascade, foreign key (time_slot_id) references timeslot on delete no action, foreign key (building, room_number) references classroom on delete set null);create table teaches ( ID varchar(5), course_id varchar(8), sec_id varchar(8), semester varchar(6), year numeric(4,0), primary key (ID, course_id, sec_id, semester, year), foreign key (course_id, sec_id, semester, year) references section on delete cascade, foreign key (ID) references instructor on delete set null);create table instructor ( ID varchar(5), name varchar(20) not null, dept_name varchar(20), salary numeric(8,2) check (salary >10000), primary key (ID), foreign key (dept_name) references department on delete set null );Then, I added data to instructor and section with the follow. Side note, I had to go in and manually set the time_slot_id as a primary key to avoid getting an error.
INSERT INTO classroom VALUES ('Innovation Hall', '101', 10);INSERT INTO classroom VALUES ('Innovation Hall', '327', 30);INSERT INTO classroom VALUES ('Exploratory Hall', '202', 20);INSERT INTO classroom VALUES ('Research Hall', '302', 20);INSERT INTO classroom VALUES ('Arts Center', '212B', 100);INSERT INTO classroom VALUES ('Research Hall', '310', 30);INSERT INTO classroom VALUES ('Innovation Hall', '121', 10);INSERT INTO classroom VALUES ('Innovation Hall', '321', 20);INSERT INTO classroom VALUES ('Arts Center', '120A', 100);INSERT INTO classroom VALUES ('Exploratory Hall', '231', 20);INSERT INTO classroom VALUES ('Innovation Hall', '220', 30);INSERT INTO department VALUES ('CDS', 'Research Hall', 100000);INSERT INTO department VALUES ('Music', 'Arts Center', 70000);INSERT INTO department VALUES ('History', 'Arts Center', 50000);INSERT INTO department VALUES ('Geography', 'Exploratory Hall', 60000);INSERT INTO department VALUES ('Biology', 'Exploratory Hall', 85000);INSERT INTO department VALUES ('Physics', 'Innovation Hall', 90000);INSERT INTO department VALUES ('Math', 'Exploratory Hall', 55000);INSERT INTO course VALUES ('CDS-101', 'Intro to CDS', 'CDS', 3);INSERT INTO course VALUES ('CDS-130', 'Computing for Scientists', 'CDS', 3);INSERT INTO course VALUES ('CDS-302', 'Databases', 'CDS', 3);INSERT INTO course VALUES ('CDS-303', 'Data Mining', 'CDS', 3);INSERT INTO course VALUES ('MUS-100', 'Fundamentals of Music', 'Music', 3);INSERT INTO course VALUES ('HIS-101', 'History of Western Civilization', 'History', 3);INSERT INTO course VALUES ('GGS-101', 'Major World Regions', 'Geography', 4);INSERT INTO course VALUES ('BIO-101', 'Intro to Biology', 'Biology', 3);INSERT INTO course VALUES ('BIO-301', 'Genetics', 'Biology', 4);INSERT INTO course VALUES ('PHY-101', 'Intro to Physics', 'Physics', 3);INSERT INTO course VALUES ('PHY-403', 'Quantum Mechanics', 'Physics', 4);INSERT INTO course VALUES ('MAT-110', 'Probabilities', 'Math', 3);INSERT INTO course VALUES ('MAT-114', 'Calculus', 'Math', 4);INSERT INTO prereq VALUES ('CDS-130', 'CDS-101');INSERT INTO prereq VALUES ('MAT-114', 'MAT-110');INSERT INTO prereq VALUES ('PHY-403', 'PHY-101');INSERT INTO prereq VALUES ('CDS-302', 'CDS-130');INSERT INTO prereq VALUES ('CDS-302', 'PHY-403');INSERT INTO prereq VALUES ('CDS-303', 'CDS-302');INSERT INTO prereq VALUES ('CDS-303', 'MAT-114');INSERT INTO instructor VALUES ('11111', 'Turing', 'CDS', 950000);INSERT INTO instructor VALUES ('11112', 'Widom', 'CDS', 100000);INSERT INTO instructor VALUES ('12121', 'Mozart', 'Music', 75000);INSERT INTO instructor VALUES ('22222', 'Heraclitus', 'History', 65000);INSERT INTO instructor VALUES ('12345', 'Eratosthenes', 'Geography', 55000);INSERT INTO instructor VALUES ('54321', 'Crick', 'Biology', 88000);INSERT INTO instructor VALUES ('33333', 'Newton', 'Physics', 80000);INSERT INTO instructor VALUES ('44444', 'Euler', 'Math', 77000);INSERT INTO instructor VALUES ('55555', 'Euclid', 'Math', 77000);INSERT INTO timeslot VALUES ('A', 'M', 8, 0 , 9, 15);INSERT INTO timeslot VALUES ('B', 'M', 10, 0 , 11, 15);INSERT INTO timeslot VALUES ('C', 'T', 8, 0 , 9, 15);INSERT INTO timeslot VALUES ('D', 'T', 10, 0 , 11, 15);INSERT INTO timeslot VALUES ('E', 'T', 11, 15 , 12, 30);INSERT INTO timeslot VALUES ('F', 'W', 9, 0 , 10, 15);INSERT INTO timeslot VALUES ('G', 'R', 8, 0 , 10, 15);INSERT INTO timeslot VALUES ('H', 'R', 15, 0 , 16, 15);INSERT INTO timeslot VALUES ('I', 'F', 9, 0 , 10, 15);INSERT INTO section VALUES ('CDS-101', '1', 'Fall', 2019, 'Research Hall', '310', 'A');INSERT INTO section VALUES ('CDS-130', '1', 'Fall', 2019, 'Innovation Hall', '121', 'B');INSERT INTO section VALUES ('CDS-302', '1', 'Fall', 2019, 'Innovation Hall', '327', 'C');INSERT INTO section VALUES ('CDS-302', '2', 'Spring', 2019, 'Innovation Hall', '321', 'C');INSERT INTO section VALUES ('MUS-100', '1', 'Fall', 2019, 'Arts Center', '120A', 'A');INSERT INTO section VALUES ('HIS-101', '1', 'Fall', 2019, 'Arts Center', '212B', 'B');INSERT INTO section VALUES ('GGS-101', '1', 'Fall', 2019, 'Exploratory Hall', '202', 'D');INSERT INTO section VALUES ('BIO-101', '2', 'Fall', 2019, 'Exploratory Hall', '231', 'E');INSERT INTO section VALUES ('PHY-403', '1', 'Spring', 2019, 'Innovation Hall', '220', 'F');INSERT INTO section VALUES ('BIO-101', '2', 'Fall', 2020, 'Exploratory Hall', '231', 'C');INSERT INTO section VALUES ('PHY-403', '1', 'Spring', 2020, 'Innovation Hall', '220', 'D');I didn’t have a problem. Finally, I tried to run this:
INSERT INTO teaches VALUES ('11111', 'CDS-101', '1', 'Fall', 2019);INSERT INTO teaches VALUES ('11112', 'CDS-130', '1', 'Fall', 2019);INSERT INTO teaches VALUES ('12121', 'MUS-100', '1', 'Fall', 2019);INSERT INTO teaches VALUES ('54321', 'BIO-101', '2', 'Fall', 2019);INSERT INTO teaches VALUES ('33333', 'PHY-403', '1', 'Spring', 2019);INSERT INTO teaches VALUES ('44444', 'MAT-114', '2', 'Fall', 2019);The error occurred on the last line. I always get:
Result: FOREIGN KEY constraint failed
At line 1: (Note: I tried re-running it by itself afterwards, thus the “Line 1”)
INSERT INTO teaches VALUES (‘44444’, ‘MAT-114’, ‘2’, ‘Fall’, 2019);
I checked over each constraint, looked at each column, and couldn’t figure it out. I even went in and entered the data manually in the “Browse Data” tab within DB Browser Lite; while I was able to enter the first 4 values, when I try to enter anything for year, I get the same error in a popup box. Even when I click in the box, leave it blank, then try to click out, I get the same error. See image.
Please assist… I’m lost at this point and quite frustrated.
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Answer
There are two things here:
- the issue, and
- how to work out what the issue is.
Let’s start with 2).
The error message is:
Result: FOREIGN KEY constraint failed
At line 1:
INSERT INTO teaches VALUES (‘44444’, ‘MAT-114’, ‘2’, ‘Fall’, 2019);
That tells us to look at the foreign keys defined on the teaches table.
There are 2:
- ID references the ID in instructor table (aside: maybe call this instructor_id instead of ID, it’ll make more sense in 6 weeks when you come back to look at it).
- course_id, sec_id, semester, year reference the section table.
There is, in your data, an instructor with ID ‘44444’, so that’s probably not the problem.
But it doesn’t look like there’s a row in section with 'MAT-114', '2', 'Fall', 2019 and that is likely your problem.
Note also that there’s not one for ‘MTH-114’ like in the image, either.