raiseerror() 的问题

Question

what I want to do is to create a stored procedure that executes insert statement.There is a possibility the execution to fail because of a check constraint for the table Employee.In that case I want to handle a user-defined error.Obviously the following procedure is not working properly because it always raises my error,but not only when insertion fails.

EXEC sp_addmessage 50001, 16, N'Title must be one of the following - Captain,Engineer,Flight-attendant,Purser,First-officer';

CREATE PROCEDURE InsertIntoEmployee

 @firstName nvarchar(30),
 @familyName nvarchar(30),
 @title nvarchar(50), 
 @address nvarchar(50), 
 @chiefID int , 
 @salary money ,
 @FK_IDCrew int,
 @FK_DepartmentID int 

AS
BEGIN 
declare @err_num int;
declare @err_sev int;
declare @err_msg int;

begin try
insert into Employee(firstName, familyName, title, address, chiefID, salary, FK_IDCrew,
FK_DepartmentID)
values(@firstName, @familyName, @title, @address, @chiefID, @salary, @FK_IDCrew,
@FK_DepartmentID);

raiserror(50001,16,1);
END try 
begin catch
set  @err_num=ERROR_NUMBER();
set @err_sev=ERROR_SEVERITY();
set @err_msg=ERROR_STATE();
raiserror(@err_num,@err_sev,@err_msg);
end catch 
end
GO

Answer 1

In this case:

• Title should be a lookup to another table and a foreign key
• In the CATCH block you can trap the FK constraint violation separately if you want...
• ...but you'd only allow rows from the new table in your client so I wouldn't personally
• No need for a sys.messages entry

Your code will also always hit the RAISERROR too which doesn't add any value,

Answer 2

1. I hope that the dimensions mentioned in the parameter list is sycn with table columns length.

2. Before insertion , You should check take care of following points.

   Check the existence of @FK_IDCrew value in it's table.

   Check the existence of @FK_DepartmentID value in it's table.

It should be like below.

If Not Exists(Select IDCrewColumnName From Table Where columnName = @FK_IDCrew)
Begin
    return here from the stored procedure.
End

In case any of them fails to meet the conditions, you should show some user friendly message to user that

(a) Crew ID , you are going to insert, either deleted or does not exists in the database.

(b) DepartmentID , you are going to insert, either deleted or does not exists in the database.

In this way the probability of error will also come to an end.