On Linux Plesk server if while adding mysql user or the database you are getting error as follows
Connection to the database server has failed: Table ‘mysql.servers’ doesn’t exist.
The issue indicates that the mysql version on the server needs up-gradation. The error can be found in /var/lib/mysqld.log
If it shows error as
114517 17:19:42 [ERROR] Can’t open and lock privilege tables: Table ‘mysql.servers’ doesn’t exist
114517 17:19:42 [ERROR] Column count of mysql.proc is wrong. Expected 20, found 16. Created with MySQL 50045, now running 50156. Please use mysql_upgrade to fix this error.
You may upgrade the mysql version on plesk server using the below command
mysql_upgrade -uadmin -p`cat /etc/psa/.psa.shadow`
Now restart the mysql service daemon on the server and you shall not get any errors