Oracle SQL Execution Process

1.sql Execution Process

1> parsing (determining whether an object exists, whether there are permission queries, semantic parsing, checking the cache for the same SQL, and so on)

2> optimization (CBO determines the optimization mode, determines the access path, the join sequence, the process through a number of comprehensive factors to estimate the various ways of resource consumption, the selection of the lowest consumption of excellent)

3> generating QEP (query execution plan: querying execution Plan)

4> Execute QEP, return result

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Oracle SQL Execution Process