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This article will explain in detail what are the stages of the query execution process of the MySQL SQL statement. The editor thinks it is very practical, so I share it with you for reference. I hope you can get something after reading this article.

1. Syntax analysis phase: after lexical and syntactic analysis, the SQL query sentence is transformed into a query tree st_select_lex and passed to the optimizer, and the semantics expressed by SQL is checked.

two。 Generate logical query execution plan phase: the optimizer traverses each relationship in the query tree, determines whether the relationship is a constant table, finds available indexes for each relationship, and uses the relationship

Algebraic principles and heuristic rules for logical query optimization (such as eliminating subqueries, eliminating outer joins, etc.).

3. Generate physical query execution plan phase: the optimizer sorts the tables of each join, and then solves the optimal path of multi-table join, using the index to calculate each relationship as much as possible.

Cost, find the least expensive path and save it to the best_positions of the JOIN class.

4. Execute the query execution plan phase: transmit the query execution plan to the executor for execution.

This is the end of this article on "what are the stages of MySQL SQL query execution process?". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it out for more people to see.

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