Question

I am working on an assignment for class where I have to take an ERD and create SQL statements to capture the relations. I am asking if the SQL statements I have created capture these relationships. In particular, I believe that “Dependent” is a weak entity and I do not know how to capture this relationship.

The ERD: https://i.stack.imgur.com/lkL1E.jpg

Here are my SQL statements:

CREATE TABLE Employees (
    ssn INTEGER, salary REAL, phone VARCHAR(24), PRIMARY KEY (ssn))

CREATE TABLE Departments (
    dno INTEGER, dname VARCHAR(150), budget REAL, PRIMARY KEY (dno), 
    managerid INTEGER, FOREIGN KEY (managerid) REFERENCES Employees (ssn))

CREATE TABLE Works_in (
    eid INTEGER, did INTEGER, PRIMARY KEY (ssn, did), FOREIGN KEY (ssn) 
    REFERENCES  Employees(eid), FOREIGN KEY (did) REFERENCES Dept (did))

CREATE TABLE Child (
    parentssn INTEGER, name VARCHAR(50), age INTEGER, FOREIGN KEY (parentssn)   REFERENCES Employees (ssn))

If it is not acceptable to post homework questions, please feel free to delete this.

I appreciate any and all help.

Thank you!

Answer 1

You did a good try.
Works_In is a relationship not a table.
So every employee will have a departmentid which references the department table.

CREATE TABLE Employees (
    ssn INTEGER, salary REAL, phone VARCHAR(24),deptno INTEGER, PRIMARY KEY (ssn),
FOREIGN KEY (parentdept) REFERENCES Departments(dno))

CREATE TABLE Departments (
    dno INTEGER, dname VARCHAR(150), budget REAL, PRIMARY KEY (dno), 
    managerid INTEGER, FOREIGN KEY (managerid) REFERENCES Employees (ssn))


CREATE TABLE Child (
    parentssn INTEGER, name VARCHAR(50), age INTEGER, FOREIGN KEY (parentssn)   
REFERENCES Employees (ssn))