sql exists
Checks for the existence of any record within the subquery, returning true if
one or more records are returned.
Example: Lists any dealerships with a deal finance percentage less than 10.
SELECT dealership_name
FROM dealerships
WHERE EXISTS (SELECT deal_name FROM deals WHERE
dealership_id = deals.dealership_id AND finance_
percentage < 10);if not exists in sql
At first glance your original attempt seems pretty close. I'm assuming that clockDate is a DateTime fields so try this:
IF (NOT EXISTS(SELECT * FROM Clock WHERE cast(clockDate as date) = '08/10/2012')
AND userName = 'test')
BEGIN
INSERT INTO Clock(clockDate, userName, breakOut)
VALUES(GetDate(), 'test', GetDate())
END
ELSE
BEGIN
UPDATE Clock
SET breakOut = GetDate()
WHERE Cast(clockDate AS Date) = '08/10/2012' AND userName = 'test'
END
Note that getdate gives you the current date. If you are trying to compare to a date (without the time) you need to cast or the time element will cause the compare to fail.
If clockDate is NOT datetime field (just date), then the SQL engine will do it for you - no need to cast on a set/insert statement.
IF (NOT EXISTS(SELECT * FROM Clock WHERE clockDate = '08/10/2012')
AND userName = 'test')
BEGIN
INSERT INTO Clock(clockDate, userName, breakOut)
VALUES(GetDate(), 'test', GetDate())
END
ELSE
BEGIN
UPDATE Clock
SET breakOut = GetDate()
WHERE clockDate = '08/10/2012' AND userName = 'test'
END
As others have pointed out, the merge statement is another way to tackle this same logic. However, in some cases, especially with large data sets, the merge statement can be prohibitively slow, causing a lot of tran log activity. So knowing how to logic it out as shown above is still a valid technique.Copyright © 2021 Codeinu
Forgot your account's password or having trouble logging into your Account? Don't worry, we'll help you to get back your account. Enter your email address and we'll send you a recovery link to reset your password. If you are experiencing problems resetting your password contact us
