Question

I am trying to learn mysql properly. When i have a query using 2 tables, Do i need to write table names before the field name all the time?

This is the one i have got

SELECT 
owner.title, owner.forename, owner.surname,
pet.name, pet.breed
FROM
owner,pet
WHERE
owner.owner_id = pet.owner_id
ORDER BY
owner.surname ASC, pet.name ASC

if i do this way is it ok aswell?

SELECT 
title, forename, surname,
name, breed
FROM
owner,pet
WHERE
owner.owner_id = pet.owner_id
ORDER BY
surname ASC, name ASC 

Answer 1

Since 1992, this:

FROM
  owner,pet
WHERE
  owner.owner_id = pet.owner_id

is (by SQL-92 standards) written as:

FROM
    owner
  JOIN                         --- or the equivalent: INNER JOIN
    pet
      ON owner.owner_id = pet.owner_id

---

To answer your question, I would prefer the first choice (modified as above) over the second, mainly for readibility. Someone else may have to read your code (or you, after a few days or months) and knowing which table every column belongs can be useful:

SELECT 
  owner.title, owner.forename, owner.surname,
  pet.name, pet.breed
FROM
    owner
  JOIN
    pet
      ON owner.owner_id = pet.owner_id
ORDER BY
  owner.surname ASC, pet.name ASC

Another reason is to catch the case you (or someone) later adds (or renames) columns on the tables and you have a “name clash” which will make your query either give error and stop working or give different than expected results.

---

You could also use aliases, like this:

SELECT 
  o.title, o.forename, o.surname,
  p.name, p.breed
FROM
    owner AS o
  JOIN
    pet AS p
      ON o.owner_id = p.owner_id
ORDER BY
  o.surname ASC, p.name ASC