in a procedure want to increment a four digit number to 1

Hi,
Refer this link[^]. This will help you a lot.

Here I modified same thing for you.
Create a User Defined Function:

CREATE FUNCTION udf_ZeroPaddingAndConcat (
	 @Id INT,
	 @Length INT,
	 @PaddingChar CHAR(1) = '0'
)
RETURNS NVARCHAR(MAX)
AS
BEGIN
RETURN (
	SELECT RIGHT(REPLICATE(@PaddingChar, @Length) + CAST(@Id as nvarchar(10)), @Length)
)
END
GO

Create the Table accordingly:

CREATE TABLE CustomIdentityTable
(
	 Id int IDENTITY(1,1) NOT NULL,
	 StringSequence as dbo.udf_ZeroPaddingAndConcat(CAST(Id as nvarchar(10)),6,'0'),
	 BookName nvarchar(250),
	 BookDescription nvarchar(max)
)

Now Insert Data:

INSERT INTO CustomIdentityTable VALUES('test', 'test')

--Amit

1. you can store it as a string then fetch the character at 3rd place(0123).
2. Change this character to integer.
3. Incerement this number.
Programmatically you can do like this,

1. str.charAt(3);
2. int num = Integer.parseInt(str.charAt(3));
3. num++