如何将不同的记录从一个表追加到另一个表 [英] How to append distinct records from one table to another

问题描述

当主表可能有重复项时，如何仅将主表中的不同记录追加到另一个表中。示例-我只希望较小的表中有不同的记录，但我需要将记录插入/追加到较小的表中已有的记录。

How do I append only distinct records from a master table to another table, when the master may have duplicates. Example - I only want the distinct records in the smaller table but I need to insert/append records to what I already have in the smaller table.

推荐答案

忽略任何并发问题：

insert into smaller (field, ... )
select distinct field, ... from bigger
except
select field, ... from smaller;

您也可以将其重新命名为联接：

You can also rephrase it as a join:

insert into smaller (field, ... )
select distinct b.field, ... 
from bigger b
left join smaller s on s.key = b.key
where s.key is NULL

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