Log Switching

Analytic function have all sorts of uses, and the lag() and lead() functions are among my favourites. I always like to remind people of the sorting overheads involved with analytic functions – but if you are prepared to accept the overhead the simplicity of comparing ‘current’ rows with ‘earlier’ or ‘later’ rows using lag() or lead() is a tremendous coding benefit.

Tuning Updates

Consider the following update statement:

update
        /*+ index(t1 t1_n1) */
        t1
set
        n1 = 0,
        n2 = n2 + 1,
        status = 'X'
where
        n1 > 100
and     status = 'A'
;