[GitHub] [incubator-shardingsphere] kimmking edited a comment on issue #4947: Is there any way to traverse tables in the specified order by Schema & Table Route

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kimmking edited a comment on issue #4947: Is there any way to traverse tables in the specified order by Schema & Table Route
URL: https://github.com/apache/incubator-shardingsphere/issues/4947#issuecomment-604309108
 
 
   @GolderGao
   
   1. How to know which one with data, and which one without data? If you know the data with its month is 3, you can direct query with `select * from  t_msg_20_3 where ...`, ShardingSphere support this sql.
   2. The 12 sharding tables is the same to ShardingSphere engine, no one is specially prior of others. If in your business semantics, they have an order to process one by one, I suggestion in native sql way. And Actually broadcasting 12 sharding tables will be parallelly query and merged, it's faster than one by one queries for several times.
   
   In our further plan, query optimization is a big blueprint. 
   As your case above, I recommend optimization by rewriting `union all` with the same database rather than `broadcast` or `one by one query`.

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