Question

TRAIN_ID TRAIN_NO SRC_DATE   COACH_ID ASSIGN_COACH_FLAG USER_ID DATE_ADDED              CH_NUMBER USER_TYPE
-------- -------- ---------- -------- ----------------- ------- ----------------------- --------- ---------
 6442 12014    2017-05-14 -        A                 psaini  2017-05-16 15:20:18.262         1 TS 
 6442 12014    2017-05-14 C1       T                 psaini  2017-05-16 15:20:18.326         1 TS 
 6442 12014    2017-05-14 C10      T                 psaini  2017-05-16 15:20:18.33          1 TS 
 6442 12014    2017-05-14 C11      T                 psaini  2017-05-16 15:20:18.334         1 TS 
 6442 12014    2017-05-14 C12      T                 psaini  2017-05-16 15:20:18.337         1 TS 
 6442 12014    2017-05-14 C13      T                 psaini  2017-05-16 15:20:18.341         1 TS 
 6442 12014    2017-05-14 C14      T                 psaini  2017-05-16 15:20:18.345         1 TS 
 6442 12014    2017-05-14 C2       T                 psaini  2017-05-16 15:20:18.349         1 TS 
 6442 12014    2017-05-14 C3       T                 psaini  2017-05-16 15:20:18.353         1 TS 
 6442 12014    2017-05-14 C4       T                 psaini  2017-05-16 15:20:18.357         1 TS 
 6442 12014    2017-05-14 C5       T                 psaini  2017-05-16 15:20:18.361         1 TS 
 6442 12014    2017-05-14 C6       T                 psaini  2017-05-16 15:20:18.364         1 TS 
 6442 12014    2017-05-14 C7       T                 psaini  2017-05-16 15:20:18.368         1 TS 
 6442 12014    2017-05-14 C8       T                 psaini  2017-05-16 15:20:18.372         1 TS 
 6442 12014    2017-05-14 C9       T                 psaini  2017-05-16 15:20:18.376         1 TS 
 6442 12014    2017-05-14 E1       T                 psaini  2017-05-16 15:20:18.379         1 TS 
 6442 12014    2017-05-14 E2       T                 psaini  2017-05-16 15:20:18.383         1 TS

这是表数据。

结果我想要的是

TRAIN_NO       COACH_ID                     -
 12014          C1  
            C10 
            C11 
            C12 
            C13 
            C14 
            C2  
            C3  
            C4  
            C5  
            C6  
            C7  
            C8  
            C9  
                E2

查询我正在使用

select distinct train_no, coach_id 
from table

请帮助我，为什么结果不符合要求。

Answer 1

select * from traindetails;

输出：

TRAINID COACHNAMES
12014        c1
12014       c2
12014       c3
12014       c4
12014       c5
12014       c6
12014       c7
12014       c8
12014       c9
12014       c10

根据您的要求，查询将如下：

SELECT  a.COACHNAMES as coah_names ,
             CASE 
                WHEN a.rnk = 1 THEN a.TRAINID
                ELSE NULL
            END AS TRAIN_ID 
  FROM (
                SELECT a.*,
                    RANK() OVER(PARTITION BY a.TRAINID ORDER BY a.COACHNAMES ) rnk
                    FROM traindetails a
                ) a

输出如下：

COAH_NAMES  TRAIN_ID
c1          12014
c10 
c2  
c3  
c4  
c5  
c6  
c7  
c8  
c9

我在sql查询中做错了什么

1 个答案: