Insert data based on non existence and different criteria's [closed] - sql

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I'm trying to add a row to my table only on two conditions but when inserting it retrieves error and I cannot figure it out
Create PROC [dbo].[setvisitorqueue]
#pid bigint = null , #vid int = NULL ,#regdate nvarchar(50) =NULL
AS
declare #queNum int =null
set #queNum = (select max([ticketNo]) + 1 from [dbo].[queue] where [ticketdate]= GetDate())
if( #queNum is null) begin set #queNum=1 end
Declare #Tktt int = null
set #Tktt = (select count(queue.ticketid) from queue where (queue.pid = #pid )and (queue.ticketdate = GetDate()) and (queue.vid = #vid and queue.checked = 0))
if (#Tktt is null )
begin insert into queue (vid , pid , ticketNo , ticketdate ) Values (#Vid,#pid,#queNum,#regdate ) end
Its not working for me.

Answer 1

Can you try it simple way like this?
CREATE PROC [dbo].[setvisitorqueue]
#pid BIGINT = null,
#vid INT = NULL,
#regdate NVARCHAR(50) = NULL
AS
IF (
SELECT COUNT(ticketid)
FROM [dbo].[queue]
WHERE checked = 0 and pid = #pid and vid = #vid and ticketdate = GetDate()
) = 0
INSERT INTO [dbo].[queue](vid pid, ticketdate, ticketNo )
SELECT #Vid, #pid, #regdate, ticketNo = IsNull(MAX([ticketNo]),0) + 1
FROM [dbo].[queue]
WHERE [ticketdate]= GetDate();
RETURN;
GO
In this code I've done following:
Improved readability by Caps, intend, spaces, etc.
Eliminated variables - you do not need them in that code You do not
need to calculate a "TicketNo" in the beginning if it won't be used.
So, it will be calculated if needed within IF statement.
You do not need to use BEGIN-END on every transaction, single
request IS a transaction
Not sure what your error was, but your procedure won't do anything just because when you do "COUNT" it returns a number. That means your "#Tktt" variable would never be NULL.
I guess your intention is to run the Insert statement when it is no records found and compared "COUNT" query to "0" value.

Answer 2

Here is your SP with all the issues I spotted corrected with comments, and with best practices added. As noted by the other answer you can probably simplify things. I have just aimed to correct existing issues.
-- NOTES: Keep your casing and layout consistent
-- Always terminate statements with a semi-colon
-- Don't add un-necessary brackets, they just clutter the code
-- You also have a concurrency issue:
-- if this proc is called twice at the same time you could issue the same ticket number twice
create proc [dbo].[setvisitorqueue]
(
#pid bigint = null,
#vid int = null,
-- Only every use a datetime/date datatype to store a datatime/date. Datetime2 is the current standard. Change precision to suit.
#regdate datetime2(0) = null
)
as
begin
-- Always start your SP with
set nocount, xact_abort on;
declare #queNum int = null;
set #queNum = (
select max([ticketNo]) + 1
from dbo.[queue]
-- This seems very unlikely to happen? It has to match down to the fraction of a second.
where [ticketdate] = getdate()
);
if #queNum is null begin
set #queNum = 1;
end;
declare #Tktt int = null;
-- #Tktt will *never* be null after this, it may be zero though.
set #Tktt = (
select count(*)
from dbo.[queue]
where pid = #pid
-- This seems very unlikely to happen? It has to match down to the fraction of a second.
and ticketdate = getdate()
and vid = #vid and checked = 0
);
-- Handle 0 or null just in case
-- if #Tktt is null -- THIS IS WHAT PREVENTED YOUR INSERT
if coalesce(#Tktt,0) = 0
begin
insert into dbo.[queue] (vid, pid, ticketNo, ticketdate)
values (#Vid, #pid, #queNum, #regdate);
end;
-- Always return the status of the SP, 0 means OK
return 0;
end;