How to change the series of zeroes in a computed column - sql-server

Question

I am using the below T-SQL to create a table with a computed column which gives me IDs in 'BID(The Year)-0000'. The issue is that I would like to reset the series of zeros in the ID when the year is changed.For example, the last ID in the table is BID2017-0923 when the year is changed I want the series to be reset for example 'BID2018-0001'.
Here is the T-SQL which currently I am using.
CREATE TABLE Books
(
ID INT IDENTITY(1,1) NOT NULL PRIMARY KEY,
IDCreateDate DATETIME NOT NULL DEFAULT GETDATE(),
BookID AS ('BID' + LTRIM(YEAR(IDCreateDate)) + '-' + RIGHT('0000' + LTRIM(ID), 4)),
ISBN VARCHAR(32),
BookName NVARCHAR(50),
AuthorName NVARCHAR(50),
BLanguage VARCHAR(50),
StaId int,
StuId int,
CatNo int
);
UPDATE:
Furthermore, I would like the ID col to remembers its last id based on the year it has.For example, the last id in the column is BID2017-0920 when I change the year to 2010, it has to reset the number series for example BID2010-0001 but when I switch back the year to 2017, I don't want the series to be reset rather I want it to start from BID2017-0921.

Answer 1

Edit#1: I've updated my solution according to latest OP's comments
/*
CREATE TABLE dbo.CustomSequence (
Name VARCHAR(50) NOT NULL,
Prefix VARCHAR(10) NOT NULL,
LastValue VARCHAR(50) NULL, -- All generated values will have following pattern: PrefixYYYY-SeqvNumber
LastYear SMALLINT NOT NULL,
CONSTRAINT PK_CustomSequence_Name_LastYear PRIMARY KEY (Name, LastYear),
LastNumber SMALLINT NULL
);
GO
-- Config OrderSequence 2014
INSERT dbo.CustomSequence (Name, Prefix, LastValue, LastYear, LastNumber)
VALUES ('BookSequence', 'BID', NULL, 2014, 1)
GO
-- Config OrderSequence 2017
INSERT dbo.CustomSequence (Name, Prefix, LastValue, LastYear, LastNumber)
VALUES ('BookSequence', 'BID', NULL, 2017, 1)
GO
*/
-- Generating new seq
-- IN Parameters
DECLARE #CustomSequenceName VARCHAR(50) = 'BookSequence'
DECLARE #Year SMALLINT = 2017 --YEAR(GETDATE())
DECLARE #LenOfNumber TINYINT = 4
-- End of IN Parameters
-- OUT Parameters
DECLARE #GeneratedValue VARCHAR(50)
-- End of OUT Parameters
UPDATE s
SET LastNumber = IIF(LastValue IS NULL, LastNumber, LastNumber + 1) + IIF(LastNumber = REPLICATE('9', #LenOfNumber), 1/0, 0),
#GeneratedValue = LastValue = Prefix + LTRIM(#Year) + '-' + RIGHT(REPLICATE('0', #LenOfNumber) + LTRIM(IIF(LastValue IS NULL, LastNumber, LastNumber + 1)), #LenOfNumber)
FROM dbo.CustomSequence s
WHERE s.Name = #CustomSequenceName
AND s.LastYear = #Year
-- End of Generating new seq
SELECT #GeneratedValue
SELECT * FROM dbo.CustomSequence
--> BID2017-0001, BID2017-0002, BID2017-0003, ...
Note#1: This solution work with pessimistic concurrency control (default behavior of SQL Server Database Engine)
Note#2: If we are reaching 10000 following piece of code
... IIF(LastNumber = 9999, 1/0, 0) ...
will raise an exception
Msg 8134, Level 16, State 1, Line 30
Divide by zero error encountered.
The statement has been terminated.
Note#3: UPDATE statement could be encapsulated into a stored procedure with #CustomSequenceName VARCHAR(50) as input parameter and #GeneratedValue VARCHAR(50) OUTPUT as OUT[PUT] parameter.
Note#4: #LenOfNumber allows to customize length of sequential number (default is 4)
Edit#2:
UPDATE statement could be replaced with following combination of INSERT + UPDATE statements:
SET XACT_ABORT ON
BEGIN TRAN
IF NOT EXISTS(SELECT * FROM dbo.CustomSequence s WITH(HOLDLOCK) WHERE s.Name = #CustomSequenceName AND s.LastYear = #Year)
BEGIN
INSERT dbo.CustomSequence (Name, Prefix, LastValue, LastYear, LastNumber)
VALUES (#CustomSequenceName, #Prefix, NULL, #Year, 1)
END
UPDATE s
SET LastNumber = IIF(LastValue IS NULL, LastNumber, LastNumber + 1) + IIF(LastNumber = REPLICATE('9', #LenOfNumber), 1/0, 0),
#GeneratedValue = LastValue = Prefix + LTRIM(#Year) + '-' + RIGHT(REPLICATE('0', #LenOfNumber) + LTRIM(IIF(LastValue IS NULL, LastNumber, LastNumber + 1)), #LenOfNumber)
FROM dbo.CustomSequence s WITH(HOLDLOCK)
WHERE s.Name = #CustomSequenceName
AND s.LastYear = #Year
COMMIT