Don't understand why am I getting Error 1215: Foreign key can not be added

Question

I am having a problem creating a database table. I have Done Something like:

CREATE TABLE STREAM( STREAM_ID INT AUTO_INCREMENT NOT NULL PRIMARY KEY, STREAM_NAME VARCHAR(100) NOT NULL, TOTAL_SEM INT NOT NULL )Engine=InnoDB;

and then:

CREATE TABLE SEMESTER( STREAM_ID INT AUTO_INCREMENT NOT NULL, SEMESTER INT NOT NULL, SUB_NAME VARCHAR(100) NOT NULL, SUB_CODE VARCHAR(100) NOT NULL, PRIMARY KEY(STREAM_ID,SUB_CODE), CONSTRAINT STUDENT_STREAM_FK5 FOREIGN KEY (STREAM_ID) REFERENCES STREAM(STREAM_ID) )Engine=InnoDB;

It creates the Database Tables very well. But When I create another Table referencing the SUB_CODE in SEMESTER table it gives me Error: 1215:

CREATE TABLE SUBJECT( Q_NO INT AUTO_INCREMENT NOT NULL, SUB_CODE VARCHAR(100) NOT NULL, SEMESTER VARCHAR(100) NOT NULL, SET_NO INT NOT NULL, Q_TYPE VARCHAR(100) NOT NULL, QUESTION VARCHAR(200) NOT NULL, CHOICE_1 VARCHAR(30), CHOICE_2 VARCHAR(30), CHOICE_3 VARCHAR(30), CHOICE_4 VARCHAR(30), CORRECT VARCHAR(30), ANSWER VARCHAR(30), MARKS FLOAT, PRIMARY KEY(Q_NO,SUB_CODE), CONSTRAINT STUDENT_SEMESTER_FK6 FOREIGN KEY (SUB_CODE) REFERENCES SEMESTER(SUB_CODE) )Engine=InnoDB;

In that case while creating SUBJECT table it gives Error:1215. I don't understand, I have created the Table SEMESTER the same way I am tryng to create SUBJECT, then why it is not working? I am using MySQL Server 5.6.

Please Help! Thanks in Advance.

Answer 1

I Solved it anyway. Just made it like:

CREATE TABLE SUBJECT( Q_NO INT AUTO_INCREMENT NOT NULL PRIMARY KEY, SUB_CODE VARCHAR(100) NOT NULL REFERENCES SEMESTER(SUB_CODE), SEMESTER VARCHAR(100) NOT NULL, SET_NO INT NOT NULL, Q_TYPE VARCHAR(100) NOT NULL, QUESTION VARCHAR(200) NOT NULL, CHOICE_1 VARCHAR(30), CHOICE_2 VARCHAR(30), CHOICE_3 VARCHAR(30), CHOICE_4 VARCHAR(30), CORRECT VARCHAR(30), ANSWER VARCHAR(30), MARKS FLOAT )Engine=InnoDB;

I ignored making the SUB_CODE the primary key. And its done. Needed it to be the foreign key of the SEMESTER table anyway!