merge 3 mysql tables into one with no duplicates
SELECT tt0.number
     , tt1.`stuff 1`
     , tt1.`stuff 2`
     , tt2.`data 2`
     , tt2.`data 5`
     , tt3.`info 1`
     , tt3.`info 4`
FROM (   SELECT t1.number FROM t1
       UNION DISTINCT
         SELECT t2.number FROM t2
       UNION DISTINCT
         SELECT t3.number FROM t3
     ) tt0
LEFT JOIN t1 tt1 ON tt0.number = tt1.number
LEFT JOIN t2 tt2 ON tt0.number = tt2.number
LEFT JOIN t3 tt3 ON tt0.number = tt3.number


This query assumes the number field is primary or at least unique key in each table.

UPDATE:


  Unfortunately this gave me errors saying that there were duplicate entries for number


If You got error You describe that is NOT MySQL error.

http://www.sqlfiddle.com/#!9/22d82dc/1