SELECT event_id, 
       user_id 
FROM   user_interaction ui 
WHERE  user_id NOT IN (SELECT user_id 
                       FROM   users); 

SELECT event_type, 
       Count(event_type) AS event_count 
FROM   user_interaction ui 
WHERE  user_id NOT IN (SELECT user_id 
                       FROM   users) 
GROUP  BY event_type 
ORDER  BY event_count DESC; 

SELECT event_id, 
       user_id, 
       event_type, 
       event_time, 
       Count(*) 
FROM   user_interaction ui 
GROUP  BY event_id, 
          user_id, 
          event_type, 
          event_time 
HAVING Count(*) > 1 

SELECT users.country, 
       Count(*) 
FROM   user_interaction ui 
       JOIN users 
       ON users.user_id = ui.user_id 
WHERE  event_type = 'VIEW' 
GROUP  BY users.country; 

SELECT age, 
       ui.event_type, 
       Count(ui.event_type) AS event_count 
FROM   users 
       JOIN user_interaction ui 
       ON ui.user_id = users.user_id 
WHERE  event_type IN ( 'CLICK', 'VIEW' ) 
GROUP  BY age, 
          ui.event_type 
HAVING Count(ui.event_type) > 5 
       AND ui.event_type = 'VIEW' 
       OR Count(ui.event_type) > 10 
       AND ui.event_type = 'CLICK';

CREATE TABLE account_invoice_records AS 
SELECT ih.invoice_number , 
       ih.account_number , 
       ih.invoice_created_date , 
       ih.invoice_due_date , 
       ii.product_number , 
       ii.net_amount , 
       ii.tax_amount 
FROM   invoice_headers ih -- 10m+ records 
JOIN   invoice_items ii   -- 100m+ records where 1=2 
and    ih.account_number = 1234;