MySQL combined query Union

Some time ago, according to the demand, the Youtou plan was separately separated into a new table. When looking at SVN, I found that the colleague's combined query is to query the data of each table, and then use array_merge to merge, and then use array_multisort, array_colomn and array_unique Combination to sort the composition, although it is also a solution to the problem, but if you think of using MySQL's Union, it may be faster and better.

First look at a picture to get familiar with the results of each query

After looking at the above picture, I basically have an understanding of the use of this.

reference reading

• MySQL learning -- the usage of join and union
• MySQL must know: Combined query (Union)
• MySQL UNION operator
• MySQL UNION and UNION ALL syntax and usage
• mysql union, union all combine two result sets
• UNION Syntax