sql server查找同一表的行之间的差异

我有一个表employees，对于给定的empid，我想列出时间、用户名以及与上一次相比发生的变化。同样对于列'req_type'，我想为0写普通，为1写重要，为值2写紧急

empid   Time                   req_type     token    requester   username    comment
------------------------------------------------------------------------------------------
10      05-01-2014 10:04:00     0             10      grusel       ann
10      05-01-2014 11:11:00     1              8                   ben       check site www:\\abc.com
10      05-01-2014 10:10:00     0              2                   ann 
12      06-01-2014 13:00:01     0              2       Jeena       bill      check www:\\someerror.com
12      07-02-2014 14:00:00     1              6        Mike       bill

Select语句应该为empid=10提供3行，如下所示

Time                    Username          Changed
---------------------------------------------------------------------------
05-01-2014 11:11:00     ben          'req_type' updated from (normal) to (important), 
                                     'token' updated from 2 to 8,
                                     'requester' deleted,
                                     'comment' added check site www:\\abc.com
05-01-2014 10:10:00     ann          'token' updated from 10 to 2,
                                     'requester' added grusel
05-01-2014 10:04:00     ann           First entry

Time                    Username          Changed
----------------------------------------------------------------------------
7-02-2014 14:00:00     bill           'req_type' updated from (normal) to (important),
                                      'token' changed from 2 to 6,
                                      'requester' changed from Jeena to Mike,
                                      'comment' deleted
6-01-2014 13:00:01      bill           First entry

类似地，Select语句应该为empid=12提供2行，如下所示

Time                    Username          Changed
---------------------------------------------------------------------------
05-01-2014 11:11:00     ben          'req_type' updated from (normal) to (important), 
                                     'token' updated from 2 to 8,
                                     'requester' deleted,
                                     'comment' added check site www:\\abc.com
05-01-2014 10:10:00     ann          'token' updated from 10 to 2,
                                     'requester' added grusel
05-01-2014 10:04:00     ann           First entry

Time                    Username          Changed
----------------------------------------------------------------------------
7-02-2014 14:00:00     bill           'req_type' updated from (normal) to (important),
                                      'token' changed from 2 to 6,
                                      'requester' changed from Jeena to Mike,
                                      'comment' deleted
6-01-2014 13:00:01      bill           First entry

---

这是一个部分答案，我们必须将最终输出转换为由emp id分隔的文本

CREATE TABLE emp (id int , [time] datetime, req_type int, token int )

INSERT INTO emp VALUES (1, GETDATE(), 0,1)
INSERT INTO emp VALUES (1, GETDATE()-1, 1,1)
INSERT INTO emp VALUES (1, GETDATE()-2, 1,3)

;WITH cte AS
(

SELECT *, ROW_NUMBER() OVER( PARTITION BY id ORDER BY time asc) rn  FROM emp 

),cte2 AS ( 
SELECT c2.*, CASE WHEN c.req_type != c2.req_type THEN 'Req changed from'+CONVERT(VARCHAR,c2.req_type)+' to '+CONVERT(VARCHAR,c.req_type)     ELSE '' END AS reqc, 
CASE WHEN c.token != c2.token THEN 'Token changed from' +CONVERT(VARCHAR,c2.token)+' to '+CONVERT(VARCHAR,c.token) ELSE '' END AS tokenc
 FROM cte c INNER join cte c2 ON c2.rn+1 = c.rn
 )

 SELECT id,time,req_type,reqc+tokenc AS changes FROM cte2 

---

粘贴在您的尝试，我们可以帮助您调整它。您还提到了2个RDBMS，是哪一个？请共享您迄今为止尝试过的SQL。在empid和行_编号-1上将表自身连接起来，然后应用您的业务规则来构造更改后的值。使用cte AS会产生编译错误。在最后一句话中，reqc+tokenc是什么意思？好的，而不是；使用cts作为语句，现在更改为select*from select*，td asc rn from employee AS cte根据id顺序将行数超额分配，但现在它在select*，行数语句上给出了语法错误