question

I want to create a procedure which would create a serial number using a stored procedure. I have three tables: **Table 1:** create table ItemTypes ( ItemTypeID int not null primary key, ItemType varchar(30) ) **Table 2:** create table ItemBatchNumber ( ItemBatchNumberID int not null primary key, ItemBatchNumber varchar(20), ItemType varchar(30), ) **Table 3:** create table ItemMfg ( ManufactureID int not null primary key, ItemBatchNumberID int foreign key references ItemBatchNumber(ItemBatchNumberID), MfgDate datetime ) For each Item Type there are several Item batch number. Now, first 3 digit of serial no is xyz. 4 digit of serial no should be Item Type(e.g if Item type is 'b' then serial no should be xyzb). 5 digit of serial no should be like this: In a day, for first Item batch number of a Item type, 5th digit should be 1 and it will remain 1 for that day.For the next different Item batch number it should be 2 and it will remain 2 for that day. Same rule applied for next day and other item type. e.g suppose 'b' Item Type has 3 Item batch number WB101,WB110,WB231. If today someone select WB110(Item batch number) of 'b' Item Type first then Serial No should be xyzb1 and it will remain xyzb1 for today for WB110. Now if someone select WR101 next then Serial No should be xyzb2 for today. Tomorrow which Item batch number of 'b' Item type will be selected first, for that batch number and that type serial no should be xyzb1. Same rule applied for other item type. I have tried till now: create procedure Gen_SerialNumber ( @IitemType varchar(30), @ItemBatchNumber varchar(30), @Date datetime, @fifthDigit int ) AS Begin set @IitemType=(Select ItemType from ItemBatchNumber where ItemBatchNumber=@ItemBatchNumber) Declare @SerialNumber varchar(20) Set @SerialNumber= 'xyz'+''+@IitemType+''+CAST( (Select COUNT(distinct ItemBatchNumber)from ItemBatchNumber,ItemMfg where MfgDate=@Date and ItemBatchNumber=@ItemBatchNumber and ItemTypeID=@IitemType) as varchar (10) ) Set @fifthDigit=SUBSTRING(@SerialNumber,5,1) if (@fifthDigit !=1) set @fifthDigit=1 else set @fifthDigit=@fifthDigit+1 Select 'SN: xyz'+''+@IitemType+''+@fifthDigit end I am new to SQL. 4rth digit of SN is generated correctly from my code. Please give me some idea on generating 5th digit and let me know if you have any doubt. Thanks in advance.