The DROP MASK RULE syntax is used to drop existing mask rule.
DropMaskRule ::=
'DROP' 'MASK' 'RULE' ifExists? ruleName (',' ruleName)*
ifExists ::=
'IF' 'EXISTS'
ruleName ::=
identifier
ifExists clause used for avoid Mask rule not exists error.DROP MASK RULE t_mask, t_mask_1;
ifExists clauseDROP MASK RULE IF EXISTS t_mask, t_mask_1;
DROP, MASK, RULE
