SQL

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 

union all query in sql

SELECT * from employee
UNION
SELECT * from students

union vs union all in sql

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 

union and union all difference

UNION: only keeps unique records
UNION ALL: keeps all records, including duplicates

SELECT City FROM student  
UNION  
SELECT City FROM student2

SELECT City FROM student  
UNION ALL
SELECT City FROM student2

union all in sql

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

union and union all

select null
union all
select null