The DROP BROADCAST TABLE RULE syntax is used to drop broadcast table rule for specified broadcast tables
DropBroadcastTableRule ::=
  'DROP' 'BROADCAST' 'TABLE' 'RULE' ifExists? tableName (',' tableName)* 
ifExists ::=
  'IF' 'EXISTS'
tableName ::=
  identifier
tableName can use the table of existing broadcast rules;ifExists clause is used for avoid Broadcast rule not exists error.DROP BROADCAST TABLE RULE t_province, t_city;
ifExists clauseDROP BROADCAST TABLE RULE IF EXISTS t_province, t_city;
DROP, BROADCAST, TABLE, RULE
