select * from performance_schema.users
limit 1;
select * from performance_schema.users
where user='FOO';
insert into performance_schema.users
set user='FOO',
current_connections=1, total_connections=2;
ERROR 42000: INSERT command denied to user 'root'@'localhost' for table `performance_schema`.`users`
update performance_schema.users
set current_connections=12;
ERROR 42000: UPDATE command denied to user 'root'@'localhost' for table `performance_schema`.`users`
update performance_schema.users
set current_connections=12 where user like "FOO";
ERROR 42000: UPDATE command denied to user 'root'@'localhost' for table `performance_schema`.`users`
delete from performance_schema.users
where total_connections=1;
ERROR 42000: DELETE command denied to user 'root'@'localhost' for table `performance_schema`.`users`
delete from performance_schema.users;
ERROR 42000: DELETE command denied to user 'root'@'localhost' for table `performance_schema`.`users`
LOCK TABLES performance_schema.users READ;
ERROR 42000: SELECT, LOCK TABLES command denied to user 'root'@'localhost' for table `performance_schema`.`users`
UNLOCK TABLES;
LOCK TABLES performance_schema.users WRITE;
ERROR 42000: SELECT, LOCK TABLES command denied to user 'root'@'localhost' for table `performance_schema`.`users`
UNLOCK TABLES;
#
# MDEV-25325 column_comment for performance_schema tables
#
select column_name, column_comment 
from information_schema.columns 
where table_schema='performance_schema' and table_name='users';
column_name	column_comment
USER	The connection's client user name for the connection, or NULL if an internal thread.
CURRENT_CONNECTIONS	Current connections for the user.
TOTAL_CONNECTIONS	Total connections for the user.