I think you need to increment @scanning_day within the loop, at the moment the while
condition will never be met because @scanning_day
remains constant as @var_period_start
. e.g.
SET @scanning_day = dateadd(dd, 1, @scanning_day);
So your full script would become:
CREATE VARIABLE @var_period_start datetime;
CREATE VARIABLE @var_period_end datetime;
CREATE VARIABLE @scanning_day datetime;
SET @var_period_start = '2013-08-17';
SET @var_period_end = '2013-08-31';
SET @scanning_day = @var_period_start;
while @scanning_day <= dateadd(dd,0,@var_period_end)
begin
UPDATE VIEWING_17to31_aug_server
SET A.calculated_scaling_weight = B.calculated_scaling_weight
FROM VIEWING_17to31_aug_server AS A
LEFT JOIN sk_prod.viq_viewing_data_scaling AS B
ON A.ACCOUNT_NUMBER = B.ACCOUNT_NUMBER
AND A.VIEWING_DAY = B.ADJUSTED_EVENT_START_DATE_VESPA
AND A.VIEWING_DAY = @SCANNING_DAY;
SET @scanning_day = dateadd(dd, 1, @scanning_day);
End