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面试题:MySQL的union all和union有什么区别、MySQL有哪几种join方式(阿里面试题)[通俗易懂]
2022-07-01 20:21:00 【全栈程序员站长】
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面试题:MySQL的union all和union有什么区别、MySQL有哪几种join方式(阿里面试题)
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MySQL的union all和union有什么区别:
UNION:合并时去除重复记录
UNION ALL:合并时不去除重复记录
格式:
创建两张表:
UNION 连接查询语句:
结果:
UNION All 连接查询语句:
结果:
注意:被合并的两个结果:列数、列类型必须相同。
mysql连接方式:https://www.cnblogs.com/2-NARUTO-2/p/7989143.html
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