如果要union all在每个查询中使用列，则必须具有相同的类型。C3必须转换为varchar，因为它c1是varchar。请尝试以下解决方案
create table "tab1" ("c1" varchar(max));
create table "tab2" ("c3" integer);
insert into tab1 values(N'asd'), (N'qweqwe');
insert into tab2 values(123), (345);
select
c_newname as myname
from
(
select "c1" as c_newname from "tab1"
union all
select cast("c3" as varchar(max)) from "tab2"
) as T_UNI;
我替换"tab3"为"tab1"-我认为这是拼写错误。
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