A SQL query searching for rows that satisfy Column1 <= X <= Column2 is very slow

Question

I am using a MySQL DB, and have the following table:

CREATE TABLE SomeTable (
  PrimaryKeyCol BIGINT(20) NOT NULL,
  A BIGINT(20) NOT NULL,
  FirstX INT(11) N         


        

Answer 1

So, I dont have enough data to be sure of the run time. This will only work if column P is unique? In order to get two indexes working, I created two indexes and the following query...

Index A - FirstX, P, Y, Z
Index B - P, LastX

This is the query

select A.P, A.Y, A.Z 
from 
    (select P, Y, Z from asdf A where A.firstx <= 185000 ) A
    join 
    (select P from asdf A where A.LastX >= 185000 ) B
    ON A.P = B.P

For some reason this seemed faster than

select A.P, A.Y, A.Z 
from asdf A join asdf B on A.P = B.P
where A.firstx <= 185000 and B.LastX >= 185000