sql_table.txt

Fact Table :
songplay_id - serial PRIMARY KEY
start_time  - date
user_id     - int
level       - varchar
song_id     - varchar
artist_id   - varchar
session_id  - int
location    - varchar
user_agent  - text

Dimesion Tables :
1) users :
user_id     - int
first_name  - varchar
last_name   - varchar
gender      - char(1)
level       - varchar

2) songs :
song_id     - varchar
title       - varchar
artist_id   - varchar
year        - smallint
duration    - float(5)

3) artists :   
artist_id   - varchar
name        - text
location    - varchar
latitude    - float(6)
longitude   - float(6)

4) time :      
start_time  - date
hour        - int
day         - int
week        - int
month       - int
year        - int
weekday     - text


The COALESCE() function returns the first non-null value in a list.