oracle创建表之前判断表是否存在，如果存在则删除已有表

DROP TABLE IF EXISTS sys_area;

CREATE TABLE sys_area
(
	id varchar(64) NOT NULL COMMENT ‘编号‘,
	parent_id varchar(64) NOT NULL COMMENT ‘父级编号‘,
	parent_ids varchar(2000) NOT NULL COMMENT ‘所有父级编号‘,
	name varchar(100) NOT NULL COMMENT ‘名称‘,
	sort decimal(10,0) NOT NULL COMMENT ‘排序‘,
	code varchar(100) COMMENT ‘区域编码‘,
	type char(1) COMMENT ‘区域类型‘,
	create_by varchar(64) NOT NULL COMMENT ‘创建者‘,
	create_date datetime NOT NULL COMMENT ‘创建时间‘,
	update_by varchar(64) NOT NULL COMMENT ‘更新者‘,
	update_date datetime NOT NULL COMMENT ‘更新时间‘,
	remarks varchar(255) COMMENT ‘备注信息‘,
	del_flag char(1) DEFAULT ‘0‘ NOT NULL COMMENT ‘删除标记‘,
	PRIMARY KEY (id)
) COMMENT = ‘区域表‘;

declare 
      num   number;
begin 
	select count(1) into num from user_tables where table_name = upper(‘sys_area‘) ; 
	if num > 0 then 
		execute immediate ‘drop table sys_area‘ ; 
	end if; 
end;

-- 区域表
CREATE TABLE sys_area
(
	id varchar2(64) NOT NULL,
	parent_id varchar2(64) NOT NULL,
	parent_ids varchar2(2000) NOT NULL,
	name nvarchar2(100) NOT NULL,
	sort number(10,0) NOT NULL,
	code varchar2(100),
	type char(1),
	create_by varchar2(64) NOT NULL,
	create_date timestamp NOT NULL,
	update_by varchar2(64) NOT NULL,
	update_date timestamp NOT NULL,
	remarks nvarchar2(255),
	del_flag char(1) DEFAULT ‘0‘ NOT NULL,
	PRIMARY KEY (id)
);