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This article is about what logical query processing means in mysql. The editor thought it was very practical, so I shared it with you as a reference. Let's follow the editor and have a look.

Query processing can be divided into logical query processing and physical query processing.

Logical query processing indicates what results the execution of the query should produce.

Physical query processing represents how the mysql database got the result.

The methods of the two queries may be completely different, but the results must be the same.

1. Logical query processing

In SQL, the first clause to be processed is always the FROM clause.

/ / example / / the preceding sequence number indicates the order of execution (8) SELECT (9) DISTINCT (1) FROM (3) JOIN (2) ON (4) WHERE (5) GROUP BY (6) WITH {CUBE | ROLLUP} (7) HAVING (10) ORDER BY (11) LIMIT

You can see that the first execution is FROM and the last is LIMIT. Each operation produces a virtual table that serves as an input for processing. These virtual tables are transparent to the user, and only the virtual tables generated in the last step will be returned to the user.

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