SQL查詢A表有數據，而B表沒數據

准備表和測試數據

create table A(
	id varchar2(10),
  name varchar2(20)
);
create table B(
	id varchar2(10),
  age number
);

insert into A values (101,'zs');
insert into A values (102,'ls');
insert into A values (103,'ww');

insert into B values (101,20);
insert into B values (106,30);
insert into B values (104,23);

需求：選出A有，B沒有的ID

方式1：遍歷B表的所有ID

select id from A where id not in (select id from B)

方式2：左連接

• 左表中沒有和右表匹配的，右表的值會以null填充

select A.*,B.* from A left join B on A.id=B.id where b.id is null