MySQL连接具有相同值的行

Question

Table Scores

ID SCORE Year_1 Year_2 Year_3

1 ---- A ------ 1 ------ 0 ------ 0

1 ---- C ------ 0 ------ 0 ------ 1

2 ---- B ------ 1 ------ 1 ------ 0

2 ---- B ------ 0 ------ 0 ------ 1

First I want to join the rows on ID when the score is the same, so that in the example below ID 2 has one row.

ID SCORE Year_1 Year_2 Year_3

1 ---- A ------ 1 ------ 0 ------ 0

1 ---- C ------ 0 ------ 0 ------ 1

2 ---- B ------ 1 ------ 1 ------ 1

But is it also possible to remove the score column and put the score in the different year-columns as below?

ID Year_1 Year_2 Year_3

1 ---- A ------ 0 ------ C

2 ---- B ------ B ------ B

=========================================================================

one problem I have after using the command in the answer, I loose scores. When the table is like this and there are multiple scores in one year:

ID SCORE Year_1 Year_2 Year_3

1 ---- A ------ 1 ------ 0 ------ 0

1 ---- B ------ 1 ------ 0 ------ 0

1 ---- C ------ 0 ------ 0 ------ 1

2 ---- B ------ 1 ------ 1 ------ 0

2 ---- B ------ 0 ------ 0 ------ 1

---

I won't get as below, but one score appearing and loose other(s):

ID Year_1 Year_2 Year_3

1 ---- A,B ---- 0 ------ C

2 ---- B ------ B ------ B

Answer 1

try this

SELECT id
      ,score
      ,Max(year_1) year_1
      ,Max(year_2) year_2
      ,Max(year_3) year_3
 FROM scores
 GROUP BY id,score

and the second one :

SELECT id
      ,group_concat(year_1) year_1
      ,group_concat(year_2) year_2
      ,group_concat(year_3) year_3
  FROM (
    SELECT id
         , CASE WHEN Max(year_1)=1 THEN Max(score) END AS year_1
         , CASE WHEN Max(year_2)=1 THEN Max(score) END AS year_2
         , CASE WHEN Max(year_3)=1 THEN Max(score) END AS year_3
      FROM scores
     GROUP BY id ,score
) as tbl2
GROUP BY id