Writing a Stored Procedure If/Else to create error message - sql

Question

I am trying to create a stored procedure with an if/else statement that will result in a Text message if the wrong CustomerID is entered into the stored procedure. As it is now it will only give me a print line when there is nothing entered in the CustomeID.
Create proc spCustOrder
#CustomerID VarChar(10),
#StartDate SmallDateTime = null,
#EndDate SmallDateTime = NUll
as
Begin
iF #CustomerID > 0
Select Distinct OrderID, OrderDate
from Customer C join CustOrder CO on CO.CustomerID = C.CustomerID
where C.CustomerID = #CustomerID and
OrderDate >= Isnull(#startDate,'1900-01-01') and
OrderDate <= IsNull(#EndDate, getDate( ))
Else
Print 'Please enter a CustomerID'
end
Basically what i am unclear on is what should i use instead of the "0" in this "#CustomerID > 0" to make the program function. i tried using CustomerID or C. and CO.CustomerID but it says that there is an error with using that command.

Answer 1

Try
IF Exists(
SELECT DISTINCT OrderID, ...
)
ELSE
PRINT ...
END
Also, you typically want to return an ID or true/false value from stored procedures and do any printing or IO in the routine that calls the proc; avoid doing IO in the proc itself.

Answer 2

Your query as written doesn't seem to require the Customers table, so the query can be written as:
Select OrderID, OrderDate
from CustOrder CO
where CO.CustomerID = #CustomerID and
OrderDate >= Isnull(#startDate,'1900-01-01') and
OrderDate <= IsNull(#EndDate, getDate( ));
You then want to print something when there are no rows in the table. I would suggest using a temporary table for storing the intermediate results so they don't have to be calculated twice. The result is something like this:
Create procedure spCustOrder (
#CustomerID VarChar(10),
#StartDate SmallDateTime = null,
#EndDate SmallDateTime = NUll
)
as Begin
Select OrderID, OrderDate
into #tmp
from CustOrder CO
where CO.CustomerID = #CustomerID and
OrderDate >= Isnull(#startDate,'1900-01-01') and
OrderDate <= IsNull(#EndDate, getDate( ));
if exists (select 1 from #tmp)
begin
select *
from #tmp;
end
else
Print 'Please enter a CustomerID'
end; -- spCustOrder

Answer 3

I have used SQL Server's RAISERROR function to throw an error if user doesnt pass a CustomerID.
RETURN keyword will stop the code execution there and exit, no further lines of code will be executed after the RETURN keyword. i.e if the value for #CustomerID is null or 0 and control enters the IF Block.
Create proc spCustOrder
#CustomerID VarChar(10) = NULL,
#StartDate SmallDateTime = null,
#EndDate SmallDateTime = NUll
AS
BEGIN
SET NOCOUNT ON;
IF (#CustomerID IS NULL OR #CustomerID = 0)
BEGIN
RAISERROR('Please enter a CustomerID',16,1)
RETURN;
END
Select Distinct OrderID, OrderDate
from Customer C join CustOrder CO
on CO.CustomerID = C.CustomerID
where C.CustomerID = #CustomerID
and OrderDate >= Isnull(#startDate,'1900-01-01')
and OrderDate <= IsNull(#EndDate, getDate( ))
END

Answer 4

To be honest I would do it completely different. you can use code like:
ALTER PROCEDURE name
#CustomerID (uniqueidentifier) - varchar is very bad solution for your performance
#date1 DATE,
#date2 DATE,
#result INT OUTPUT=0 - use it as output parameter and handle text in app code
AS
BEGIN TRAN
IF EXISTS (your SELECT query. You don't need DISTINCT)
BEGIN
-- if exists do something smart. I don't know... UPDATE TABLE
IF ##error<>0
BEGIN
SET #result=1 --there was an error executing query in something smart
END
ELSE - from IF EXISTS statement
BEGIN
SET #result=2 --means no records found
END
IF #result=1
BEGIN
RETURN 1 --you know that this is error from your application code
ROLLBACK TRAN --there was an error in doing something smart
END
IF #result=2
RETURN 2 -- from your application code you know that this means no users found
END
IF RETURN=0
BEGIN
RETURN 0 -- userid found and something smart done without error :)
COMMIT TRAN
END
Hope this helps. You should analyze more bit about what will you do on application level and what do you want to do on DB level.
If helped mark it if no, ping with questions

Answer 5

Try IS NULL :
Create proc spCustOrder
#CustomerID VarChar(10),
#StartDate SmallDateTime = null,
#EndDate SmallDateTime = NUll
as
Begin
iF (#CustomerID IS NULL)
Select Distinct OrderID, OrderDate
from Customer C join CustOrder CO on CO.CustomerID = C.CustomerID
where C.CustomerID = #CustomerID and
OrderDate >= Isnull(#startDate,'1900-01-01') and
OrderDate <= IsNull(#EndDate, getDate( ))
Else
Print 'Please enter a CustomerID'
end