could someone explain the sql code for many-many, many-one, and one-one??????? PLEASE USE SIMPLE TABLES AND DESCRIBE EACH LINE!!!
could someone explain the sql code for many-many, many-one, and one-one??????? PLEASE USE SIMPLE TABLES AND DESCRIBE EACH LINE!!!
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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So i was watching a breif video about converting erds into sql tables and need help understanding somethings. So in this screenshot, is this the code for establishing a relationship? ALSO, could someone explain the sql code for many-many, many-one, and one-one??????? PLEASE USE SIMPLE TABLES AND DESCRIBE EACH LINE!!!
![**Employee**
We can use `CHECK` constraints to enforce specific values or formats:
```sql
CREATE TABLE employee (
ssn CHAR(11) PRIMARY KEY,
f_name VARCHAR(40),
m_init CHAR(1),
l_name VARCHAR(50),
address VARCHAR(200),
salary MONEY,
gender CHAR(1) -- this really,
works_for_dept INTEGER NOT NULL,
FOREIGN KEY (works_for_dept) REFERENCES department(number),
CHECK(ssn LIKE '[0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]'),
CHECK(gender IN ('M', 'F', 'N', 'T', 'I', 'P'))
);
-- N=Nonbinary, T=transgender, I=intersex, P=PreferNotToAnswer
```
### Diagram Explanation
The diagram illustrates relationships in a database schema with an "Employee" table connecting to a "Department" table through the "Works_for" relationship. The lines and symbols indicate:
- An "Employee" working for a department.
- A Foreign Key constraint (`works_for_dept`) linking to a department number.
- It's a standard entity-relationship notation showing a one-to-many relationship between the tables.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F7daa69d8-205a-4b72-abf5-96966d755823%2F85f10005-6935-4da0-a5dc-b4920174ef2a%2Fw8rrsti_processed.jpeg&w=3840&q=75)
Transcribed Image Text:**Employee**
We can use `CHECK` constraints to enforce specific values or formats:
```sql
CREATE TABLE employee (
ssn CHAR(11) PRIMARY KEY,
f_name VARCHAR(40),
m_init CHAR(1),
l_name VARCHAR(50),
address VARCHAR(200),
salary MONEY,
gender CHAR(1) -- this really,
works_for_dept INTEGER NOT NULL,
FOREIGN KEY (works_for_dept) REFERENCES department(number),
CHECK(ssn LIKE '[0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]'),
CHECK(gender IN ('M', 'F', 'N', 'T', 'I', 'P'))
);
-- N=Nonbinary, T=transgender, I=intersex, P=PreferNotToAnswer
```
### Diagram Explanation
The diagram illustrates relationships in a database schema with an "Employee" table connecting to a "Department" table through the "Works_for" relationship. The lines and symbols indicate:
- An "Employee" working for a department.
- A Foreign Key constraint (`works_for_dept`) linking to a department number.
- It's a standard entity-relationship notation showing a one-to-many relationship between the tables.
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