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

You need to add another index on LastX.

The unique index FirstLastXPriority_Index (FirstX,LastX,P) represents the concatenation of these values, so it will be useless with the 'AND LastX >= ?' part of your WHERE clause.