Oracle 删表前验证表名是否存在并且删除

DECLARE num NUMBER;
BEGIN
SELECT COUNT(1) INTO num FROM USER_TABLES WHERE TABLE_NAME = UPPER(‘tableName‘) ;
IF num > 0 THEN
  EXECUTE IMMEDIATE ‘DROP TABLE tableName‘ ;
END IF;
END;

declare 
num number; 
num1 number;
num2 number;
begin 

SELECT COUNT(1) INTO num FROM USER_TABLES WHERE TABLE_NAME = UPPER(‘BAK_XX1‘) ;
SELECT COUNT(1) INTO num1 FROM USER_TABLES WHERE TABLE_NAME = UPPER(‘BAK_XX2‘) ;
SELECT COUNT(1) INTO num2 FROM USER_TABLES WHERE TABLE_NAME = UPPER(‘BAK_XX3‘) ;
if num=1 then 
execute immediate ‘drop table BAK_XX1‘; 
end if; 
if num1=1 then 
execute immediate ‘drop table BAK_XX2‘; 
end if; 
if num1=1 then 
execute immediate ‘drop table BAK_XX3‘;