Question

I am trying to update several rows from data of a specific row
THIS IS A SINGLE TABLE, ItemNum is unique
my attempt:

UPDATE myTable t, (SELECT DISTINCT width, repeat
            FROM myTable
            WHERE ItemNum='80644') t1
SET t.width = t1.width
AND SET t.repeat = t1.repeat
WHERE ItemNum='80645'
AND WHERE ItemNum='80646'

gives me an error
#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FROM myTable WHERE ItemNum='80644') t1 SET t.width' at line 2

when i run this for a single row it works
but the syntax for multiple rows seem to be the issue

UPDATE myTable t, (SELECT DISTINCT width
  FROM myTable
  WHERE ItemNum='80644') t1
SET t.width = t1.width
WHERE ItemNum='80645'

Answer 1

Should work, but it won’t give reliable results if there are more than one rows with itemnum=80644

UPDATE myTable t
join
    (SELECT DISTINCT width, repeat
            FROM myTable
            WHERE ItemNum='80644') t1
    on t.ItemNum in ('80645','80646')
SET
    t.width = t1.width,
    t.repeat = t1.repeat