====== LU06.A03 - SQL-DDL: Constraint Management ======

===== Requirements  =====
  * Work type: individual
  * Timeframe: 30 Minutes
  * Means of aid: 
      * Only teaching materials, no websearch, no use of ai.
      * [[https://www.w3schools.com/sql/trysql.asp?filename=trysql_select_columns | W3Schools | SQL Editor]]
  * Expected result: Semantically and syntactically correct SQL statements according to the requirements of the case studies. 

===== Case studies / Assignments =====
Here are five assignments, each covering a specific MySQL constraint. As usual, along with the solutions at the end (link).

===== Assignments =====

==== A: PRIMARY KEY ====
Create a table books that has a book_id as a unique identifier for each book, with book_id as the primary key. Include columns for book_title (VARCHAR) and author_name (VARCHAR). The book_id should be an integer and cannot be NULL.

==== B: AUTO INCREMENT ====
Create a table products where each product has an automatically generated, unique product_id using the AUTO_INCREMENT feature. Include columns for product_name and price.

==== C: NOT NULL ====
Create a table students that includes a student_id (INT) and a student_name (VARCHAR). Ensure that the student_name column cannot have a NULL value by applying the NOT NULL constraint.

==== D: UNIQUE ====
Create a table users that has a user_id (INT) and email (VARCHAR). Ensure that no two users can have the same email address by applying the UNIQUE constraint to the email column. 

==== E: FOREIGN KEY ====
Create two tables: one called departments and the other called employees. Each department has a department_id as its primary key. In the employees table, include a column called department_id as a foreign key that references the departments table. Ensure that every employee is linked to a department.
  
===== Solution =====
[[modul:m290:learningunits:lu05:loesungen:l03|Lösung]]


===== Vocabulary =====
^ English ^ German ^ 
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