sql_queries.py

# DROP TABLES

songplay_table_drop = "DROP TABLE IF EXISTS songplays"
user_table_drop = "DROP TABLE IF EXISTS users"
song_table_drop = "DROP TABLE IF EXISTS songs"
artist_table_drop = "DROP TABLE IF EXISTS artists"
time_table_drop = "DROP TABLE IF EXISTS time"

# CREATE TABLES

songplay_table_create = ("""
CREATE TABLE IF NOT EXISTS songplays                                               
(songplay_id SERIAL PRIMARY KEY,
start_time TIMESTAMP,
user_id VARCHAR,
level VARCHAR,
song_id VARCHAR,
artist_id VARCHAR,
session_id VARCHAR,
location VARCHAR,
user_agent VARCHAR)
""")


user_table_create = ("""
CREATE TABLE IF NOT EXISTS users
(user_id VARCHAR PRIMARY KEY,
first_name VARCHAR,
last_name VARCHAR,
gender CHAR(1),
level VARCHAR)
""")

song_table_create = ("""
CREATE TABLE IF NOT EXISTS songs
(song_id VARCHAR PRIMARY KEY,
title VARCHAR,
artist_id VARCHAR,
year INT,
duration NUMERIC)
""")

artist_table_create = ("""
CREATE TABLE IF NOT EXISTS artists
(artist_id VARCHAR PRIMARY KEY,
name VARCHAR,
location VARCHAR,
latitude NUMERIC,
longitude NUMERIC)
""")

time_table_create = ("""
CREATE TABLE IF NOT EXISTS time
(start_time TIMESTAMP PRIMARY KEY,
hour VARCHAR,
day VARCHAR,
week VARCHAR,
month VARCHAR,
year VARCHAR,
weekday VARCHAR)
""")

# INSERT RECORDS
# Remarks:
#There is no need to INSERT songplay_id as you have already made it an auto-incremented key by using the SERIAL keyword.
#Just remove it from INSERT statement.
songplay_table_insert = ("""
INSERT INTO songplays (start_time, user_id, level, song_id, artist_id, session_id, location, user_agent)
VALUES (%s, %s, %s, %s, %s, %s, %s, %s)
""")

# Remarks:
#the users table is different from other tables in that "level" could be updated. 
#Think of a free user upgraded into the paid tier - in that case, we should not insert a different row, or ignore the new record. 
#Instead, we should update `level` when there's conflict.
user_table_insert = ("""
INSERT INTO users (user_id, first_name, last_name, gender, level)
VALUES (%s, %s, %s, %s, %s)
ON CONFLICT (user_id) DO UPDATE
    SET level=EXCLUDED.level
""")

song_table_insert = ("""
INSERT INTO songs (song_id, title, artist_id, year, duration)
VALUES (%s, %s, %s, %s, %s)
ON CONFLICT (song_id) DO NOTHING
""")

artist_table_insert = ("""
INSERT INTO artists (artist_id, name, location, latitude, longitude)
VALUES (%s, %s, %s, %s, %s)
ON CONFLICT (artist_id) DO NOTHING
""")


time_table_insert = ("""
INSERT INTO time (start_time, hour, day, week, month, year, weekday)
VALUES (%s, %s, %s, %s, %s, %s, %s)
ON CONFLICT (start_time) DO NOTHING
""")

# FIND SONGS

song_select = ("""SELECT s.song_id, a.artist_id
FROM songs AS s
JOIN artists AS a
ON s.artist_id=a.artist_id
WHERE s.title=%s
    AND a.name=%s
    AND s.duration=%s
""")

# QUERY LISTS

create_table_queries = [songplay_table_create, user_table_create, song_table_create, artist_table_create, time_table_create]
drop_table_queries = [songplay_table_drop, user_table_drop, song_table_drop, artist_table_drop, time_table_drop]