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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]
2022-07-01 22:11:00 【Full stack programmer webmaster】
Hello everyone , I meet you again , I'm your friend, Quan Jun .
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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