curs-11-sql-1
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7/25/2019 curs-11-SQL-1
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26.01.2017 Mihai S.
SQL
1. Introduction
- limbaj baze de date -> Structured Query Language (Oracle SQL si No SQL- de tipnone relational: Casandra)
- MySQL sistem de gestiune a bazelor de date (soft)- SGBD in ro- DBMS data base management system- SQL Lite - mobile
Ex.: Blog - SQL de tip relational, comunica entitatile intre ele- stocam entitati:
ArticoleUseriComentarii
Tabela User:
- coloane: nume, parola - ce anume vrem sa stocam (fielduri)
- randuri (row sau entry)- in randuri (cell) avem valorile -> value- id primary key, unicitate, fiecare record va avea id unic
CRUD
SELECT Namewhere Population > 100000
from `Country`
C -> createR -> read- Select
- * (all) type of info- From
- table name- Where
- de unde cer informatia- CountryCode = ROU- ``-> apostrof sau tic, escape la row User, city etc.
- AND -> din alt camp si intervale- AS -> pt. denumire a ceea ce vreau sa-mi aduca- DISTINCT -> aduce o valoare o singura data chiar daca se repeta
- BETWEEN -> intervale, mai mare sau egal doar (interval inchis, daca iavaloarea e interval inchis pe ambele capete)
- MIN (parametru),- ORDER BY- IS NOT -> pt. diferit de !=- DESC, ASC- INNER JOIN -> impreunez valorile/datele comune, in loc de virgula- ON -> pe ce cheie comuna fac inner joinul- IN -> lista de valori (values/parametri)
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