Sorry! but what I want to ask you is 2,625,810 (219 × 110 × 109)? because row 4,5,6 are union one. Therefore, I think it should “+ 109” instead of “x 109”. Doe that make sense?

I am trying to find any reference about how to calculate the number of rows that MySQL need to go through in total.

Thank you!

You can see that in the rows column of explain output. Its 12 and 23 for the first two tables and remaining have only one row . Does that make sense?

Thanks ]]>

I am thinking that the second number (276 (12 × 23)) is not correct. ]]>