如何计算字符串＆＃39; yyyymm＆＃39;进入字符串＆＃39; yyyymm -1＆＃39;例如：计算＆＃39; 201401＆＃39;进入＆＃39; 201312＆＃39;在T-SQL中？

Question

如何将字符串'yyyymm'计算到字符串'yyyymm -1'

中

例如：在T-SQL中将'201401'计算为'201312'？

Answer 1

SQL> select * from t_flag
  2  /

EMP_NAME                   EMP_NO DEPT
-------------------------------------------------- --------- --------------------

    ROBI                        1 AGRO
    ROBI                        1 AGRO
    BORIS                       2 IT
    SID                         3 VET
    BORIS                       2 IT

    select t_flag.*,
 (case when row_number() over (partition by emp_name,emp_no,dept order by emp_name) = 1
                 then 0 else 1
            end) as GroupFlag
 from t_flag
SQL> /

EMP_NAME                                              EMP_NO DEPT                 GROUPFLAG
-------------------------------------------------- --------- -------------------- ---------
BORIS                                                      2 IT                           0
BORIS                                                      2 IT                           1
ROBI                                                       1 AGRO                         0
ROBI                                                       1 AGRO                         1
SID                                                        3 VET                          0