1st, 2nd and 3rd Normal Form (Database Normalisation) Youtube Video Questions

Question 1

What are the rules for First Normal Form? (1NF)

Answer 1

• All rows must be unique (no duplicate rows)
• Each cell must only contain a single value (not a list)
• Each value should be non divisible (can’t be split down further) AKA Atomic

Question 2

What are the rules for Second Normal Form? (2NF)

Answer 2

• Database must be in First Normal Form (1NF)
• Non partial dependency - All non-prime attributes should be fully functionally dependent on the candidate key

(Om man kan lista ut någon information i en kolumn som inte är från hela composite keyn utan bara en av primary keysen är det inte i 2NF!)

(Men verkar som att det år OK att liste ut info som inte är från compositekey hmm)

Question 3

What are the rules for Third Normal Form? (3NF)

Answer 3

• Database must bei n First & Second Normal Form
• No transitive dependency - All fields must only be determinable by the primary/composite key, not by other keys

(Man får inte lista ut information från någonting annat än compositekey (eller primary key om det bara finns en))

Question 4

What is a regular solution to make a normalization problem go away?

Answer 4

Make a new table of the columns that are problematic.