python-sql-lessons/SQL/lessons/sql_3.md

PostGres - Advanced

Lesson Objectives - important

1. Linking Tables
2. Alias
3. Indexes
4. Constraints

Lesson Objectives - good to know about

1. EER Diagrams
2. Unions
3. Truncate
4. Triggers
5. Views
6. Functions/Stored Procedures
7. Transactions
8. Locks
9. Privileges
10. Denormalization
11. Excel -> CSV -> MySQL

Important

Linking Tables

1. Some Nice Visuals
2. One to Many/Many to One Relationships
   • customer has many orders
3. One to One Relationships
   • each user has one address
   • only one person at that address
4. Many to Many Relationships
   • actors and movies
5. Self Referncing Relationships
   • customer referral

Alias

SELECT t1.column1 as col1, t2.column2 as col2
FROM table1 as t1
INNER JOIN table2 as t2
ON t1.common_filed = t2.common_field;

Indexes

1. CREATE INDEX index_name ON table_name (column_name);
2. CREATE INDEX index_name ON table_name (column1_name, column2_name);
3. use \d table_name to view indexes
4. Primary Key

Constraints

1. NOT NULL
2. Unique
3. Foreign Keys

CREATE TABLE companies(
  id          SERIAL       PRIMARY KEY,
  name        VARCHAR(16)  NOT NULL UNIQUE,
  city        VARCHAR(16)
);
INSERT INTO companies ( city ) VALUES ('Palo Alto');
CREATE TABLE people(
  id          INT          PRIMARY KEY,
  name        VARCHAR(16)  NOT NULL,
  email       VARCHAR(32)  NOT NULL UNIQUE,
  company_id  INT          REFERENCES companies(id)
);
INSERT INTO people (name, email, company_id) VALUES ('bob', 'bob@bob.com', 999)

Good to Know About

EER Diagrams

Unions

Truncate

Triggers

Views

Functions/Stored Procedures

Transactions

Locks

Privileges

Denormalization

Excel -> CSV -> MySQL

SQL Injection