union和union all的区别之后增加where
时间: 2023-10-13 07:02:52 浏览: 93
union和union all的区别是,union会自动压缩多个结果集合中的重复结果,而union all则将所有的结果全部显示出来,不管是不是重复。如果在进行union或union all操作之后增加了where条件,这个where条件会应用到整个结果集合上,对结果进行筛选。例如,如果使用union all进行两个表的合并,并增加了where条件"where id > 5",那么结果集合中只会包含id大于5的记录,不会包含其他的记录。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
#### 引用[.reference_title]
- *1* [union和union all的区别](https://blog.csdn.net/a200822146085/article/details/119545374)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v92^chatsearchT0_1"}}] [.reference_item style="max-width: 50%"]
- *2* *3* [union all和union的区别](https://blog.csdn.net/Angel_asp/article/details/123827072)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v92^chatsearchT0_1"}}] [.reference_item style="max-width: 50%"]
[ .reference_list ]