簡單，純粹的Sql查詢（擺脫重複結果）

Question

如果有人知道更好的標題，請繼續並改變它。

我知道我的嘗試是最好的mediacore，所以如果你知道一個更好的aproach請分享。我會盡量保持簡單明瞭：

我的數據庫表：

ID |  Category |  Number |  NumberInCategory | 

    1    A    31    101 
    2    B    31    107 
    3    C    31    121 
    4    A    32    191 
    5    A    33    165 
    6    B    32    156 
    7    C    32    127 

我需要什麼樣的輸出：

Number |   A   |  B  |   C  

    31    101    107    121 
    32    191    156    127 
    33    165    NULL    NULL 

我嘗試：

SELECT (SELECT DISTINCT(Number) FROM MYDB V WHERE F.ID = V.ID) AS Id, 
     (SELECT NumberInCategory FROM MYDB V WHERE F.Number = V.Number AND Category = 'A') AS CategoryA , 
     (SELECT NumberInCategory FROM MYDB V WHERE F.Number = V.Number AND Category = 'B') AS CategoryB, 
     (SELECT NumberInCategory FROM MYDB V WHERE F.Number = V.Number AND Category = 'C') AS CategoryC 
FROM MYDB F; 

我的結果：

31|101|107|121 
31|101|107|121 
31|101|107|121 
32|191|156|127 
33|165|| 
32|191|156|127 
32|191|156|127 

我只是不能找到一種方法來得到這個工作。

我有人想幫助這裏充滿了腳本https://www.tutorialspoint.com/execute_sql_online.php

BEGIN TRANSACTION; 

/* Create a table called SAMPLE */ 
CREATE TABLE MYDB(Id integer PRIMARY KEY, Category text, Number integer, NumberInCategory integer); 

/* Create few records in this table */ 
INSERT INTO MYDB VALUES(1,'A',31,101); 
INSERT INTO MYDB VALUES(2,'B',31,107); 
INSERT INTO MYDB VALUES(3,'C',31,121); 
INSERT INTO MYDB VALUES(4,'A',32,191); 
INSERT INTO MYDB VALUES(5,'A',33,165); 
INSERT INTO MYDB VALUES(6,'B',32,156); 
INSERT INTO MYDB VALUES(7,'C',32,127); 
COMMIT; 

/* Display all the records from the table */ 
SELECT * FROM MYDB; 

SELECT (SELECT DISTINCT(Number) FROM MYDB V WHERE F.ID = V.ID) AS Id, 
     (SELECT NumberInCategory FROM MYDB V WHERE F.Number = V.Number AND Category = 'A') AS CategoryA , 
     (SELECT NumberInCategory FROM MYDB V WHERE F.Number = V.Number AND Category = 'B') AS CategoryB, 
     (SELECT NumberInCategory FROM MYDB V WHERE F.Number = V.Number AND Category = 'C') AS CategoryC 
FROM MYDB F; 

編輯 簡單GROUP BY在年底做這項工作.____。

SELECT (SELECT Number FROM MYDB V WHERE F.ID = V.ID) AS Id, 
     (SELECT NumberInCategory FROM MYDB V WHERE F.Number = V.Number AND Category = 'A') AS CategoryA , 
     (SELECT NumberInCategory FROM MYDB V WHERE F.Number = V.Number AND Category = 'B') AS CategoryB, 
     (SELECT NumberInCategory FROM MYDB V WHERE F.Number = V.Number AND Category = 'C') AS CategoryC 
FROM MYDB F 
GROUP BY NUMBER; 

結果：

31|101|107|121                                                           
32|191|156|127                                                           
33|165|| 

雖然從接受的答案的形式給出（由@Gordon Linoff）是更好的。

Answer 1

可以使用條件彙總：

select number, 
     max(case when category = 'A' then numberincategory end) as a, 
     max(case when category = 'B' then numberincategory end) as b, 
     max(case when category = 'C' then numberincategory end) as c 
from t 
group by number; 

Answer 2

的SQL Server支持的語法稱爲PIVOT：

SELECT number, [A],[B],[C] 
FROM (select category, number, numberincategory from a) t 
PIVOT 
(
    SUM([numberincategory]) 
    FOR category IN ([A],[B],[C]) 
) AS pvt; 

的基本格式是：

SELECT 
    List,of,columns,that,will,form,row,headers, 
    List,of,row,values,that,form,column,headers 
FROM (
    select query that pulls ONLY the data you need for 
    row headers, column headers, and the columns you want to summarise 
)tablealias 
PIVOT 
(
    SUM/AVG/MIN/MAX/etc(column to summarise) 
    FOR category IN (List,of,row,values,that,form,column,headers) 
) AS pvt;