Understanding MySQL Explains `rows`-wise

Question

I am trying to figure out how I should consider the rowsMySQL output column explain. Here 's the MySQL documentation talking about this:

The row column indicates the number of rows MySQL thinks it should check the query.

So here are my questions:

• Regardless of its accuracy, will it be the number of records that will be checked after using indexes or earlier?
• Is it right that I need to evaluate high table optimization rows?
• Is it true that the total number of records MySQL will learn is a column product rows?
• What are the reduction strategies rows?

Answer 1

• The value of the indexes is what the DBMS will look there first, and then use the collected information to find matching rows. So - yes, it rowswill indicate how many rows will be checked after using indexes (if they are present and applicable, of course). This question means you are confusing which indexes. They are not magic, they are just a real data structure. All of them make sense to reduce the number of data lines used to execute the query.
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