Syntax:
DO expr [, expr] ...

DO executes the expressions but does not return any results. In most
respects, DO is shorthand for SELECT expr, ..., but has the advantage
that it is slightly faster when you do not care about the result.

DO is useful primarily with functions that have side effects, such as
RELEASE_LOCK().

Example: This SELECT statement pauses, but also produces a result set:

mysql> SELECT SLEEP(5);
+----------+
| SLEEP(5) |
+----------+
|        0 |
+----------+
1 row in set (5.02 sec)

DO, on the other hand, pauses without producing a result set.:

mysql> DO SLEEP(5);
Query OK, 0 rows affected (4.99 sec)

This could be useful, for example in a stored function or trigger,
which prohibit statements that produce result sets.

DO only executes expressions. It cannot be used in all cases where
SELECT can be used. For example, DO id FROM t1 is invalid because it
references a table.

As of MySQL 5.7.8, DO statement errors that previously were converted
to warnings are returned as errors.

URL: http://dev.mysql.com/doc/refman/5.7/en/do.html

