SQL存在一個表而不在另一個表中的資料，sql不在

SQL存在一個表而不在另一個表中的資料，sql不在

select a.id,a.oacode,a.custid,a.custname,a.xsz,a.salename,a.communicationtheme,a.communicationproperty,a.communicationtime,a.productmanager,'' creator,a.creator oaCreator,a.createdate,case when a.oastate='正常結束' then 3 else 0 end status from reception_flow a where  (1=1)and (a.oastate='正常結束' or a.oastate='反饋中' or a.oastate='已反饋')and (select count(1) as num from technology_support s where s.oacode=a.oacode)=0

怎用sql語句查詢：在一個表中存在而另一個表中不存在的第一條記錄？

select top 1 *
from tb2
where id not in (select [index] from tb1)
order by id
 
sql查詢一個表裡的資料在另一個表是否存在

insert into tableA
select * from tableB b where not exists(select 1 from tableA a where a.id = b.id)
insert into tableA
select * from tableB b
left join tableA a on a.id = b.id
where a.id is null
----用 not exists來判斷,left join ，其中條件為唯一性主鍵