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SQL and Data Warehousing - Database issues

3 important questions on SQL and Data Warehousing - Database issues

What is a relational scheme?

Textual representation of database tables – Primary key attributes are underlined

Examples: – Book(Bno, Author, Title) – Loan(Bno, Rno, Loan date, Return date)

Which three types of cardinality are there




  1. One-to-one (or zero-to-one)
  2. One-to-may
  3. Many-to-many (M-to-N). Often via a Bridge table. This table decomposes the M-to-N
    table in to one-to-many relationships.
Important to look at the primary key and the foreign key (= a primary key in another table).

What are Joins and which types do we have?



  1. Inner join (result = both circles)
  2. Left outer join (you have customers with order and without order)
3. Right outer join (customers with orders, and orders without customers)

4. Full outer join (customers without orders, customers with order, orders without
customers)
5. Minus (customers without orders)

The question on the page originate from the summary of the following study material:

Data Mining for Business Analytics Concepts, Techniques, and Applications with XLMiner | 9781118729243 | Galit Shmueli, et al

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