Answers for "difference between structure and union"

what is the difference between union and union all

UNION ALL:
COMBINES THE RESULT OF 2 QUERY AND
DOESN'T REMOVE DUPLICATE ROWS
AND DOESN'T SORT BY FIRST COLUMN

UNION:
COMBINES THE RESULT OF 2 QUERY AND
REMOVES DUPLICATE ROWS AND
SORTS BY FIRST COLUMN

difference between structure and union

struct [structure name]
   {
       member definition;
       member definition;
       ...
       member definition;
   };