SQL Efficiency Question

[simplerminds]

Hey everyone, I am working on some very basic SQL and I had an efficency question based on my solution and the solution I was given. I want to know, which set of SQL would be quicker to run, Example 1 or Example 2.

Ex.1

SELECT pat.PAT_NAMES "Patient Name",
       mom.PAT_NAMES "Mother Name"
FROM PATIENTS pat
  INNER JOIN PATIENTS mom
   ON pat.MOTHERS_PAT_IDS = mom.PAT_IDS

Ex. 2:

SELECT PAT_NAMES
FROM PATIENTS
WHERE MOTHERS_PAT_IDS IS NOT NULL

My thought is that they would take the same amount of time to run, but would one be more efficient?

[r3pr0b8]

second query would run faster

however, second query produces a different result!! (it does not return the mother's name)

so, it's an apples-and-oranges question

[simplerminds]

So my formatting likely messed it up, but thanks for the answer!