--下面的代码生成长度为8的编号，编号以BH开头，其余6位为流水号。
--得到新编号的函数
CREATE FUNCTION f_NextBH()
RETURNS char(8)
AS
BEGIN
    RETURN(SELECT 'BH'+RIGHT(1000001+ISNULL(RIGHT(MAX(BH),6),0),6) FROM tb WITH(XLOCK,PAGLOCK))
END
GO

--在表中应用函数
CREATE TABLE tb(
BH char(8) PRIMARY KEY DEFAULT dbo.f_NextBH(),
col int)

--插入资料
BEGIN TRAN
    INSERT tb(col) VALUES(1)
    INSERT tb(col) VALUES(2)
    INSERT tb(col) VALUES(3)
    DELETE tb WHERE col=3
    INSERT tb(col) VALUES(4)
    INSERT tb(BH,col) VALUES(dbo.f_NextBH(),14)
COMMIT TRAN

--显示结果
SELECT * FROM tb
/*--结果
BH         col 
---------------- ----------- 
BH000001  1
BH000002  2
BH000003  4
BH000004  14
--*/

------解决方案--------------------

借2楼改一下
SQL code

IF EXISTS (SELECT 1 FROM SYSOBJECTS WHERE name = 'tba')
BEGIN
    DROP TABLE tba
END
GO
IF EXISTS (SELECT 1 FROM SYSOBJECTS WHERE name = 'GetNext')
BEGIN
    DROP FUNCTION GetNext
END
GO
CREATE FUNCTION GetNext()
RETURNS VARCHAR(20)
AS
BEGIN
    RETURN(SELECT 'CK'+ RTRIM(DATEPART(YEAR,GETDATE())) + '-' + RIGHT(RTRIM(10001 + ISNULL(RIGHT(MAX(BH),4),0)),4) FROM tba WITH(XLOCK,PAGLOCK))
END
GO

--在表中应用函数
CREATE TABLE tba(
BH VARCHAR(20) PRIMARY KEY DEFAULT dbo.GetNext(),
col int)

--插入资料
BEGIN TRAN
    INSERT tba(col) VALUES(1)
    INSERT tba(col) VALUES(2)
    INSERT tba(col) VALUES(3)
    DELETE tba WHERE col=3
    INSERT tba(col) VALUES(4)
    INSERT tba(BH,col) VALUES(dbo.GetNext(),14)
COMMIT TRAN

SELECT * FROM tba

BH    col
CK2012-0001    1
CK2012-0002    2
CK2012-0003    4
CK2012-0004    14