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SQL Logical Optimization

This chapter explains some key logic rewrites to help you understand how TiDB generates the final query plan. For example, when you execute the select * from t where t.a in (select * from t1 where t1.b=t.b) query in TiDB, you will find that the IN sub-query t.a in (select t1.a from t1 where t1.b=t.b does not exist because TiDB has made some rewrites here.

This chapter introduces the following key rewrites: