BETWEEN clause versus <= AND >=

There is no difference.

Note that BETWEEN is always inclusive and sensitive to the order of the arguments.

BETWEEN '2010' AND '2005' will never be TRUE.

There is no performance difference between the two example queries because BETWEEN is simply a shorthand way of expressing an inclusive range comparison. When Oracle parses the BETWEEN condition it will automatically expand out into separate comparison clauses:

ex.

SELECT *    FROM table WHERE column BETWEEN :lower_bound AND :upper_bound  

...will automatically become:

SELECT *    FROM table WHERE :lower_bound <= column   AND :upper_bound >= column

Actually it depends on your DBMS engine.

Some database management systems will compute twice your expression (once for each comparison), and only once when you use BETWEEN.

Actually if the expression can have a non-deterministic result BETWEEN will have a different behaviour, compare the following in SQLite:

WHERE RANDOM() BETWEEN x AND y -- one random value generatedWHERE RANDOM() >= x AND RANDOM() <= y -- two distinct random values generated

This can be very time consuming if your expression is (for example) a subquery.