Interview question: what is the difference between MySQL's Union all and union, and how many join methods MySQL has (Alibaba interview question) [easy to understand]

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Interview questions ：MySQL Of union all and union What's the difference? 、MySQL With what kind of join The way ( Ali Interview questions )

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MySQL Of union all and union What's the difference? ：

UNION： Remove duplicate records when merging

UNION ALL： Duplicate records are not removed during consolidation

Format ：

Create two tables ：

UNION Join query statement ：

result ：

UNION All Join query statement ：

result ：

Be careful ： The two results of the merger ： Number of columns 、 The column type must be the same .

mysql How to connect ：https://www.cnblogs.com/2-NARUTO-2/p/7989143.html

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