Is MySQL's SLEEP() function a busy-wait? How to implement it?

No, MySQL sleep function is not busy-wait. Let us first create a table and implement the SLEEP() function −

mysql> create table DemoTable(FirstName varchar(100));
Query OK, 0 rows affected (0.57 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values('John');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable values('Adam');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable values('Bob');
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable values('Chris');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable values('Robert');
Query OK, 1 row affected (0.16 sec)

Display all records from the table using select statement. We have also set the SLEEP() function here −

mysql> select sleep(10),FirstName from DemoTable;

This will produce the following output −

+-----------+-----------+
| sleep(10) | FirstName |
+-----------+-----------+
|         0 | John      |
|         0 | Adam      |
|         0 | Bob       |
|         0 | Chris     |
|         0 | Robert    |
+-----------+-----------+
5 rows in set (50.00 sec)