Syntax:
query_expression_body EXCEPT [ALL | DISTINCT] query_expression_body
    [EXCEPT [ALL | DISTINCT] query_expression_body]
    [...]

query_expression_body:
    See 

EXCEPT limits the result from the first query block to those rows which
are (also) not found in the second. As with UNION and INTERSECT, either
query block can make use of any of SELECT, TABLE, or VALUES. An example
using the tables a, b, and c defined in [HELP INTERSECT], is shown
here:

mysql> TABLE a EXCEPT TABLE b;
+------+------+
| m    | n    |
+------+------+
|    2 |    3 |
+------+------+
1 row in set (0.00 sec)

mysql> TABLE a EXCEPT TABLE c;
+------+------+
| m    | n    |
+------+------+
|    1 |    2 |
|    2 |    3 |
+------+------+
2 rows in set (0.00 sec)

mysql> TABLE b EXCEPT TABLE c;
+------+------+
| m    | n    |
+------+------+
|    1 |    2 |
+------+------+
1 row in set (0.00 sec)

As with UNION and INTERSECT, if neither DISTINCT nor ALL is specified,
the default is DISTINCT.

DISTINCT removes duplicates found on either side of the relation, as
shown here:

mysql> TABLE c EXCEPT DISTINCT TABLE a;
+------+------+
| m    | n    |
+------+------+
|    1 |    3 |
+------+------+
1 row in set (0.00 sec)

mysql> TABLE c EXCEPT ALL TABLE a;
+------+------+
| m    | n    |
+------+------+
|    1 |    3 |
|    1 |    3 |
+------+------+
2 rows in set (0.00 sec)

(The first statement has the same effect as TABLE c EXCEPT TABLE a.)

Unlike UNION or INTERSECT, EXCEPT is not commutative---that is, the
result depends on the order of the operands, as shown here:

mysql> TABLE a EXCEPT TABLE c;
+------+------+
| m    | n    |
+------+------+
|    1 |    2 |
|    2 |    3 |
+------+------+
2 rows in set (0.00 sec)

mysql> TABLE c EXCEPT TABLE a;
+------+------+
| m    | n    |
+------+------+
|    1 |    3 |
+------+------+
1 row in set (0.00 sec)

As with UNION, the result sets to be compared must have the same number
of columns. Result set column types are also determined as for UNION.

EXCEPT was added in MySQL 8.0.31.

URL: https://dev.mysql.com/doc/refman/8.0/en/except.html

