What does it mean MATERIALIZED in the select_type column in the result of MySQL Explain closure?

Question

I just got the next result of MySQL Explain closure:

And I, unfortunately, don't understand what does it mean MATERIALIZED in the last row of the select_type column.

If somebody knows what does it mean please give me any advice to study in this question or give me the answer to it.

Valuer

#3030341 – Colous

Answer 1

It means that the result of a subquery was saved as a virtual temporary table instead of executing it for each row. This was introduced in MySQL 5.7 and speeds up some queries that were super slow before due to the fact the result of their subquery parts wasn't cached

Shanklin