--将15位身份证升级成18位的用户定义函数
CREATE FUNCTION ID15TO18 (@id15 char(15)) 
RETURNS CHAR(18) AS 
BEGIN 
   DECLARE @ID18 CHAR(18)
   
   DECLARE @S1 AS INTEGER
   DECLARE @S2 AS INTEGER
   DECLARE @S3 AS INTEGER
   DECLARE @S4 AS INTEGER
   DECLARE @S5 AS INTEGER
   DECLARE @S6 AS INTEGER
   DECLARE @S7 AS INTEGER
   DECLARE @S8 AS INTEGER
   DECLARE @S9 AS INTEGER
   DECLARE @S10 AS INTEGER
   DECLARE @S11 AS INTEGER
   DECLARE @S12 AS INTEGER
   DECLARE @S13 AS INTEGER
   DECLARE @S14 AS INTEGER
   DECLARE @S15 AS INTEGER
   DECLARE @S16 AS INTEGER
   DECLARE @S17 AS INTEGER
   DECLARE @S18 AS INTEGER
   
   SET @S1 = SUBSTRING(@ID15,1,1)
   SET @S2 = SUBSTRING(@ID15,2,1)
   SET @S3 = SUBSTRING(@ID15,3,1)
   SET @S4 = SUBSTRING(@ID15,4,1)
   SET @S5 = SUBSTRING(@ID15,5,1)
   SET @S6 = SUBSTRING(@ID15,6,1)
   SET @S7 = 1
   SET @S8 = 9
   SET @S9 = SUBSTRING(@ID15,7,1)
   SET @S10 = SUBSTRING(@ID15,8,1)
   SET @S11 = SUBSTRING(@ID15,9,1)
   SET @S12 = SUBSTRING(@ID15,10,1)
   SET @S13 = SUBSTRING(@ID15,11,1)
   SET @S14 = SUBSTRING(@ID15,12,1)
   SET @S15 = SUBSTRING(@ID15,13,1)
   SET @S16 = SUBSTRING(@ID15,14,1)
   SET @S17 = SUBSTRING(@ID15,15,1)
   
   SET @S18 = ( (@S1*7) + (@S2*9) + (@S3*10) + (@S4*5) + (@S5*8) + 
   (@S6*4) + (@S7*2) + (@S8*1) + (@S9*6) + (@S10*3) + 
   (@S11*7) + (@S12*9) + (@S13*10) + (@S14*5) + (@S15*8) + 
   (@S16*4) + (@S17*2) ) % 11
   
   SET @ID18 = SUBSTRING(@ID15,1,6) + '19' + SUBSTRING(@ID15,7,9) + 
                 CASE 
                     WHEN @S18 = 0 THEN '1'
                     WHEN @S18 = 1 THEN '0'
                     WHEN @S18 = 2 THEN 'X'
                     WHEN @S18 = 3 THEN '9'
                     WHEN @S18 = 4 THEN '8'
                     WHEN @S18 = 5 THEN '7'
                     WHEN @S18 = 6 THEN '6'
                     WHEN @S18 = 7 THEN '5'
                     WHEN @S18 = 8 THEN '4'
                     WHEN @S18 = 9 THEN '3'
                     WHEN @S18 = 10 THEN '2'
                 END
   
    RETURN @ID18
END 
GO



--调用函数
update 
    表
set 
    身份证号 = dbo.ID15TO18(身份证号)
where
    LEN(身份证号) = 15

------解决方案--------------------

SQL code
-- 15位身份证号升级为18位，适用于18xx年出生的公民
UPDATE 员工表 SET 身份证号=
  SUBSTRING(身份证号,1,6)+'18'+SUBSTRING(身份证号,7,9)+
  SUBSTRING('10X98765432',
  (
   CAST(SUBSTRING(身份证号, 1,1) AS INT)*7
  +CAST(SUBSTRING(身份证号, 2,1) AS INT)*9
  +CAST(SUBSTRING(身份证号, 3,1) AS INT)*10
  +CAST(SUBSTRING(身份证号, 4,1) AS INT)*5
  +CAST(SUBSTRING(身份证号, 5,1) AS INT)*8
  +CAST(SUBSTRING(身份证号, 6,1) AS INT)*4
  +1*2
  +8*1
  +CAST(SUBSTRING(身份证号, 7,1) AS INT)*6
  +CAST(SUBSTRING(身份证号, 8,1) AS INT)*3
  +CAST(SUBSTRING(身份证号, 9,1) AS INT)*7
  +CAST(SUBSTRING(身份证号,10,1) AS INT)*9
  +CAST(SUBSTRING(身份证号,11,1) AS INT)*10
  +CAST(SUBSTRING(身份证号,12,1) AS INT)*5
  +CAST(SUBSTRING(身份证号,13,1) AS INT)*8
  +CAST(SUBSTRING(身份证号,14,1) AS INT)*4
  +CAST(SUBSTRING(身份证号,15,1) AS INT)*2
  )
  % 11 + 1, 1)
WHERE LEN(身份证号)=15 AND SUBSTRING(身份证号,13,3) IN ('999','998','997','996')

-- 15位身份证号升级为18位，适用于19xx年出生的公民
UPDATE 员工表 SET 身份证号=
  SUBSTRING(身份证号,1,6)+'19'+SUBSTRING(身份证号,7,9)+
  SUBSTRING('10X98765432',
  (
   CAST(SUBSTRING(身份证号, 1,1) AS INT)*7
  +CAST(SUBSTRING(身份证号, 2,1) AS INT)*9
  +CAST(SUBSTRING(身份证号, 3,1) AS INT)*10
  +CAST(SUBSTRING(身份证号, 4,1) AS INT)*5
  +CAST(SUBSTRING(身份证号, 5,1) AS INT)*8
  +CAST(SUBSTRING(身份证号, 6,1) AS INT)*4
  +1*2
  +9*1
  +CAST(SUBSTRING(身份证号, 7,1) AS INT)*6
  +CAST(SUBSTRING(身份证号, 8,1) AS INT)*3
  +CAST(SUBSTRING(身份证号, 9,1) AS INT)*7
  +CAST(SUBSTRING(身份证号,10,1) AS INT)*9
  +CAST(SUBSTRING(身份证号,11,1) AS INT)*10
  +CAST(SUBSTRING(身份证号,12,1) AS INT)*5
  +CAST(SUBSTRING(身份证号,13,1) AS INT)*8
  +CAST(SUBSTRING(身份证号,14,1) AS INT)*4
  +CAST(SUBSTRING(身份证号,15,1) AS INT)*2
  )
  % 11 + 1, 1)
WHERE LEN(身份证号)=15 AND SUBSTRING(身份证号,13,3) NOT IN ('999','998','997','996')