Question

Hello i am trying to do this simple statement but i want to add a variable that comes from a select. Here is what i have.

 userEmail varChar(50) := SELECT user_id FROM users WHERE email = '[e-mail]';
        SELECT * 
        FROM iphone_alerts
        WHERE user_id =  userEmail
        AND date_added = (SELECT MAX(date_added) FROM iphone_alerts WHERE user_id = userEmail  

Do i need to use something along the lines of Declare and Begins? I am new to the sql stuff and am having trouble finding answers.

Answer 1

If you want to do this in SQL, you’d want something like

SELECT alerts.*
  FROM iphone_alerts alerts,
       users 
 WHERE alerts.user_id = users.user_id
   AND users.email = '[e-mail]'
   AND alerts.date_added = (SELECT MAX(date_added)
                              FROM iphone_alerts alerts2
                             WHERE alerts2.user_id = user.user_id)

Probably more efficient would be something like this that lets us hit the IPHONE_ALERTS table just once.

SELECT <<list of columns in IPHONE_ALERTS>>
  FROM (
    SELECT alerts.*,
           RANK() OVER (PARTITION BY alerts.user_id ORDER BY date_added DESC) rnk
      FROM iphone_alerts alerts,
           users 
     WHERE alerts.user_id = users.user_id
       AND users.email = '[e-mail]'
  )
 WHERE rnk = 1