The result of the above SQL statement will be the number 3, because the customer Smith has made 3 orders in total. If you don't specify a WHERE clause when using COUNT, your statement will simply return the total number of rows in the table, which in our case is 7:
Uses of Sleep Spindles Edit. Sleep spindles are one of several measures employed by the brain to keep a sleeper in an unconscious state. This pattern is produced during sleep to inhibit the processing of unnecessary information, which would especially interrupt stage 2 sleep.
As we make the transition from stage 1 to stage 2 sleep a number of changes occur in the EEG that signal the increasing depth of sleep. Two prominent markers of stage 2 sleep are K complexes and sleep spindles. K complexes are large waves that stand out from the background and often occur in response to environmental stimuli such as sounds in the bedroom. Sleep spindles are brief bursts of fast activity that appear something like the shape of an eye as they rapidly increase in amplitude and then rapidly decay.