An employee cannot access the company database. You check the connection variables:
Mysql> SHOW GLOBAL VARIABLES LIKE ‘%connect%’;

8 rows in set (0.00 sec)
A look at the user privileges shows:
GRANT… TO ‘bob’@’%, example.com’ WITH MAX_USER_CONNECTIONS 0;
GRANT… TO ‘key’@’%, example.com’ WITH MAX_USER_CONNECTIONS 1;
GRANT… TO ‘joe’@’%, example.com’ WITH MAX_USER_CONNECTIONS 50;
What is a valid explanation for why one of the users is unable to connect to the database?
A.
Bob has max_user_connections set to zero, which blocks all his connections
B.
Joe has exceeded the max_user_connections global limit.
C.
All users are blocked because max_user_connections is accumulated over the host account information.
D.
Kay is already connected elsewhere and attempting to log in again.
E.
Connect_timeout is too small to allow a connection to occur.
答案:D