生成3位的序列号_仅仅CASE WHEN的简单应用

SELECT TOP 200
    PNo, IDENTITY( INT,1,1 ) AS sn
INTO
    #temp1
FROM
    tbl_test 

SELECT
    CASE WHEN sn < 10 THEN '00' + CONVERT(CHAR(1), sn)
         WHEN sn >= 10
              AND sn <= 99 THEN '0' + CONVERT(CHAR(2), sn)
         WHEN sn >= 100 THEN CONVERT(CHAR(3), sn)
    END AS sn, PNo
FROM
    #temp1