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Katrina Rodzon
1,414 PointsHelp: MySQL HAVING clarification
I am working on the String function portion of the database deep dive and ran across something.
I am trying to call up a series of variables from the dataset and then filter out the usernames that are 19 or more characters in length.
The command only works if I put an alias in for username
SELECT first_name, UPPER(last_name), LOWER(email), LENGTH(username) AS username_length FROM users HAVING username_length < 19;
versus the following.
SELECT first_name, UPPER(last_name), LOWER(email), LENGTH(username) FROM users HAVING username < 19;
Any ideas why?
Thanks!!
4 Answers
Nicholas Mejia
23,800 PointsIt looks like it's not so much that it is a bad query, but more like they are trying to teach you the "proper" way to form a solid query. It's a better idea for readability and gives you more flexibility when running queries in your code.
This is a great explanation of it right here:
http://www.tutorialarena.com/mysql/mysql-as-keyword.php
Regards, homie!
Katrina Rodzon
1,414 PointsNicholas,
I actually ran the first command in MySQL Workbench and it did not return anything. It seems as though it's not correct in some way.
Nicholas Mejia
23,800 PointsUnfortunately, I have not completed the database deep dive so I am not too familiar with what the query is pulling from or what the lesson is. Which lesson is it so I can just jump in and take a look?
Katrina Rodzon
1,414 PointsIt's in the SQL Calculating...section under the STRING function lesson. It occurs within the video not the challenge.