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01-My_notes.sql
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-- This is a Single line Comments.
/*
This is a
Multi-line
Comment
*/
/* **************************************************************************************** */
/*What's SQL?
Structured Query Language (SQL) is a standart computer language for relational database management
and data manipulation.
Used to query, insert, update and modify data.
SQL ia a non-procedural language (Cannot write complete applications)
SQL is used to Read/retrieve, write and update data.
*/
/* DBA vs Data Scientist
DBA:
- Manages/governs the DB;
- Given permissions to users;
- Determines acess to data;
- Manages and create Tables;
DS:
- End user;
- Uses SQL to query and retrieve data.
*/
/* How Data Scientists uses SQL?
- Retrieve data;;
- Create their own Tables and environments;
- Write complex querys for analysis.
*/
/*Relational vs Transactional Models
Relational: Allows for easy querying and data manipulation in an easy, logicaland intuitive way;
Transactional: Operational database, e.g. insurance claims a healthcare db.
*/
/*Data Models Building Blocks
the basic model of a relational database is made up of 3 things: Entity, Attribute and relationships.
Entitys are things like: person, place, thing or event. Are distinguishable, unique amd distinct.
Are basic the rows in a table.
Attributes are the colums in a table, and are the characteritics of an entity.
Relationship describe associations among entities.
There are different types such as Many-to-many, one-to-many, one-to-one and etc.
*/
/*
ER diagrams notation to study:
Chen notation, Crow's foot notation, UML Diagram notation.
*/