searching through multiple tables with a stored procedures - sql-server

Question

I have two tables Vehicle and Vehicle return(it was spelled incorrectly in the code),I'm trying to create a stored procedure where I can enter the engine number and it would search through Vehicle and Vehicle return to see if it matches the engine number and the criteria that it is in either of the table but every time only thing that works is if the engine number isn't in either of the tables here is my code
create procedure outbound
(
#eng varchar(25)
)
AS
BEGIN
BEGIN TRAN
DECLARE #eng_num VARCHAR(25)
DECLARE #eng_num2 VARCHAR(25)
/* SELECT #eng_num= Engine_num from Vehicle where Engine_num=#eng and Status=1
SELECT #eng_num2= Engine_num from Vehicle_retuns where Engine_num=#eng
IF(#eng=#eng_num)
begin
UPDATE Vehicle SET Description_of_Vehicle='Vehicle has ben sent to Manufactory',Status=0 where Engine_num=#eng_num
end
ELSE IF(#eng=#eng_num2)
begin
UPDATE Vehicle_retuns SET purpose='Vehicle has ben sent to Manufactory',Status=0 where Engine_num=#eng_num2
end*/ the lines of code that is the error is occuring
ELSE
SELECT 'No such Engine number was found'
IF(##ERROR<>0)
BEGIN
SELECT 'An unexpected error has occur'
ROLLBACK TRANSACTION
RETURN -1
END
COMMIT TRANSACTION
END

Answer 1

Here is a rough sketch of what I think might be required here. There is no need to use an explicit transaction for a single update. Also, I would highly recommend you look at normalizing your messages instead of hard coding those long strings everywhere. Not sure you really mean to set the Description or purpose column depending on the value of status. I would rather see those be foreign keys to a lookup of values but maybe that doesn't work here. I would also recommend you not use column names like "status". Using reserved words is problematic for a number of reasons. Last but not least, you should use try/catch blocks instead of checking ##ERROR.
--EDIT--
Here is some new code that handles the fact that you really do need two updates. I missed this originally.
create procedure outbound
(
#eng varchar(25)
)
AS
BEGIN
IF EXISTS
(
SELECT Engine_num
from Vehicle
where Engine_num = #eng
UNION ALL
SELECT Engine_num
from Vehicle_retuns
where Engine_num = #eng
)
BEGIN
BEGIN TRY
BEGIN TRANSACTION
UPDATE Vehicle
SET Description_of_Vehicle = 'Vehicle has ben sent to Manufactory'
, Status = 0
where Engine_num = #eng
AND Status = 1
UPDATE Vehicle_retuns
SET purpose = 'Vehicle has ben sent to Manufactory'
, Status = 0
where Engine_num = #eng
COMMIT TRANSACTION
END TRY
BEGIN CATCH
SELECT 'An unexpected error has occurred.'
--I would prefer a message here including the error message and error number instead of just "It failed".
END CATCH
END
ELSE
SELECT 'No such Engine number was found'
END