PG中，一张表的定义如下：create table t (sn integer primary key,id integer,check(sn>0 and id<0)); 下面哪些插入语句会出现约束错误：（AB） A、insert into t values(null,-3); B、insert into t values(1,0); C、insert into t values(2,-1); D、insert into t values(3,null);