📅  最后修改于: 2022-03-11 14:55:52.179000             🧑  作者: Mango
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