Question

This answer from Bill Karwin to question 121387 worked perfectly for me..

“I see many people use subqueries or else vendor-specific features to do this, but I often do this kind of query without subqueries in the following way. It uses plain, standard SQL so it should work in any brand of RDBMS.

SELECT t1.*
FROM mytable AS t1
  LEFT OUTER JOIN mytable AS t2
    ON (t1.UserId = t2.UserId AND t1."Date" < t2."Date")
WHERE t2.UserId IS NULL;

In other words: fetch the row from t1 where no other row exists with the same UserId and a greater Date.”

However, I also need to include in the result a column from a third table (imagine another table with UserId and UserPhoneNumber columns). It feels as if it should be straightforward but it’s driving me nuts. Any help would be appreciated.

Answer 1

Simply join the third table after the LEFT JOIN:

SELECT t1.*, t3.*
FROM mytable AS t1
  LEFT OUTER JOIN mytable AS t2
    ON (t1.UserId = t2.UserId AND t1."Date" < t2."Date")
JOIN myothertable AS t3 ON t1.UserId = t3.UserId
WHERE t2.UserId IS NULL;