T-SQL Generate Unique Codes - tsql

Question

I have a table contacts.
CREATE TABLE [dbo].[Contacts](
[ContactId] [int] IDENTITY(1,1) NOT NULL,
[ContactCode] [nvarchar](10) NOT NULL, --UNIQUE
[FirstName] [nvarchar](24) NOT NULL,
[MiddleName] [nvarchar](12) NULL,
[LastName] [nvarchar](24) NOT NULL,
CONSTRAINT [PK_Contacts] PRIMARY KEY CLUSTERED
(
[ContactId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
I would like to be able to generate a 10-digit contact code from the stored procedure which should comprise of
First Two Digits of FirstName
First Digit of MiddleName(When MiddleName is not blank)
First Two or Three(When MiddleName is Blank) Digits of Last Name
Four digit number starting from zero.
Example.
John M. Denver = JOMDE-0001
John Denver = JODEN-0001
John Denver = JODEN-0002
Bob Dylan = BODYL-0001
Proposed solution could be a function which could be called from inside the stored procedure before saving the values to the table.
CREATE FUNCTION GetContactCode
(
#FirstName nvarchar(24),
#MiddleName nvarchar(12),
#LastName nvarchar(24)
)
RETURNS nvarchar(10)
AS
BEGIN
RETURN('CODE')
END
Can anybody help?

Answer 1

Using a RANKING clause is one option.
;WITH q AS (
SELECT ContactID
, ContactCode =
UPPER(
SUBSTRING(
SUBSTRING(FirstName, 1, 2)
+ ISNULL(SUBSTRING(MiddleName, 1, 1), '')
+ SUBSTRING(LastName, 1, 3)
, 1, 5)
+ '-')
FROM Contacts
)
SELECT c.*
, q.ContactCode
+ RIGHT(REPLICATE('0', 4)
+ CAST(
RANK() OVER (PARTITION BY q.ContactCode ORDER BY q.ContactID
) AS VARCHAR(4))
, 4)
FROM q INNER JOIN Contacts c ON c.ContactId = q.ContactID

Answer 2

This function should do the trick
CREATE FUNCTION GetContactCode
(
#FirstName nvarchar(24),
#MiddleName nvarchar(12),
#LastName nvarchar(24)
)
RETURNS nchar(10)
AS
BEGIN
declare #contactcode nchar(10)
select top 1 #contactcode = contactCode
from contacts
where
contactcode like left(#FirstName,2)+
case
when #MiddleName is null or #MiddleName = '' then left(#LastName,3)
else left(#MiddleName,1)+left(#LastName,2)
end+'%'
order by contactCode desc
select #Contactcode =
Upper(left(#FirstName,2)+
case
when #MiddleName is null or #MiddleName = '' then left(#LastName,3)
else left(#MiddleName,1)+left(#LastName,2)
end) + '-' +
case
when #ContactCode is null then'0001'
else replace(str(cast(right(#ContactCode,4) as int)+1,4),' ','0')
end
Return #ContactCode
END