Question

Oracle记录插入时违反唯一性约束，求SQL语句

A表由a、b两个字段构成复合主键，把B表的数据插入A表时怎么跳过A表已经有的记录

Answer 1

insert into A

select * from B where not exists (
select 1 from a where a.a=b.a and a.b=b.b
);