如何将记录从表插入到另一个而不重复 [英] How to insert records from table to another without duplicate

问题描述

我有两个表t1和t2. t1的值重复.我需要将所有记录从t1插入到t2，但是我不希望在t2中出现重复记录.我尝试了以下命令，在我看来，它似乎是正确的，运行时没有语法错误，但是问题是，它的效果为0.没有将t1中的记录插入到t2中.

I have two tables t1 and t2. t1 has duplicated values. I need to insert all records from t1 to t2, but I don't want duplicates to occur in t2. I tried the following command which seems to me correct and no syntax error when I run it but the problem, it has 0 effect. No records from t1 inserted in t2.

insert into test.t2 (name2) 
select name1 from test.t1 where NOT EXISTS (select name2 from test.t2);

有人可以帮忙吗?

推荐答案

insert into test.t2(name2) 
select distinct name1 from test.t1 where name1 NOT IN(select name2 from test.t2);

OR

insert into test.t2(name2) 
select distinct name1 from test.t1 t1 where NOT EXISTS(select name2 from test.t2 t2 where t1.name1=t2.name2);

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