A.firewalld -add-port 3306/tcp --permanentB.firewall-cmd -add-port 3306/tcp --permanentC.firewall -add-port 3306/tcp --permanentD.firewall-cmd -add-port 3306/tcp
A.firewall-cmd -add-service mysql --permanentB.firewall-cmd -add-service mysqlC.firewall-cmd -add-service mysqld --permanentD.firewalld -add-service mysql --permanent
A.where 字段=值B.having 字段=值C.from 字段=值D.select 字段=值