Forma Normala 1

postat acum 4 ani de Stefanescu Mihai in categorie SQL

Prima forma normala vine cu un set de reguli destul de standard entru organizarea structuriii unei baze de date.

    • Asigura-te ca ai o singura valoare in fiecare camp.
    • Asigura-te ca nu exista grupuri de informatii ce se repeta

Asigura-te ca exista o cheie primara.

Exemplu:

Nume Telefon 1 Telefon 2
Nume Student 0728848714 0764748627

Exemplul de mai sus este gresit pentru ca in timp ce un student are 2 numere de telefon si se potriveste perfect altul are 1 numar de telefon (lasand un camp gol), iar altul poaet avea 10 (si nu avem unde sa le bagam).

Acum probabil va ganditi sa faceti urmatorul lucru:

Nume Telefon
Nume Student 0728848714, 0764748627

Nici asa nu este corect pentru ca daca dorim sa extragem un numar de telefon pentru un student o sa extragem tot ce scrie acolo…si nici nu mai vorbesc de alte probleme ce pot aparea din cauza asta.

Acum hai sa va arat un exemplu corect.

In primul rand trebuie sa facem 2 tabele: Studenti si Telefoane:

Studenti:

ID_Student Student
1 Nume Student

Telefoane:

ID ID_Student Telefon
1 1 0728848714
2 1 0764748627

Acum Putem cate numere de telefon dorim fiecarui student fara sa ne mai facem probleme ca apar erori.

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