查詢查詢

Question

我需要小查詢的幫助。

表A： - 狀態及其內容如下。

status_id  status_descrip 
     1   held 
     2   release 
     3   WIP 

表B： - Entry是另一個有大約30個字段的表。其中2個字段指的是表A->狀態表。爲了簡單起見，我跳過其他字段並僅記下與狀態相關的字段。

entry_id  design_status   stress_status 
    1     3     1 
    2     1     2 
    3     NULL    2 
    4     3     3 
    5     NULL    1 
    6     NULL    NULL  
    7     NULL    2 

我不能改變條目的結構分裂成2代表一個作爲design_status等作爲stress_status。

現在我想從條目表中的條目用他們的描述替換狀態。所以輸出將是

entry_id  design_status_descrip   stress_status_descrip 
     1     WIP       held 
     2     held       release 
     3     NULL       release 
     4     WIP       WIP. 
     5     NULL       held 
     6     NULL       NULL 
     7     NULL       release 

在此先感謝！

編輯： -

問題用條目編輯。

謝謝你的所有迴應！

終於爲我工作的查詢，

SELECT  b.entry_id,  design_status_descrip = d.status_descrip, 
    stress_status_descrip = s.status_descrip FROM  entry AS b 
    LEFT OUTER JOIN status AS d  ON b.design_status = d.status_id 
    LEFT OUTER JOIN status AS s  ON b.stress_status = s.status_id 

不要讓我知道，如果我能改善這個查詢。

Answer 1

最簡單的方法是加入對狀態表的兩倍。我已經使用了INNER JOIN，假定您的模式中的design_status和stress_status列具有適當的約束。針對變更的要求進行編輯。

DECLARE @status TABLE 
(
    status_id INT PRIMARY KEY, 
    status_descrip VARCHAR(32) NOT NULL UNIQUE 
); 

INSERT @status SELECT 1,'held' UNION SELECT 2,'release' UNION SELECT 3,'WIP'; 

DECLARE @b TABLE 
(
    entry_id INT PRIMARY KEY, 
    design_status INT, 
    stress_status INT 
); 

INSERT @b SELECT 1,3,1 
UNION SELECT 2,1,2 
UNION SELECT 3,NULL,2 
UNION SELECT 4,3,3 
UNION SELECT 5,NULL,1 
UNION SELECT 6,NULL,NULL 
UNION SELECT 7,NULL,2; 

SELECT 
    b.entry_id, 
    design_status_descrip = d.status_descrip, 
    stress_status_descrip = s.status_descrip 
FROM 
    @b AS b 
    LEFT OUTER JOIN @status AS d 
    ON b.design_status = d.status_id 
    LEFT OUTER JOIN @status AS s 
    ON b.stress_status = s.status_id; 

Answer 2

SELECT 
    e.entry_id, 
    s1.status_descrip as design_status_descrip, 
    s2.status_descrip as stress_status_descrip 
FROM entry e, status s1, status s2 
WHERE 
    e.design_status = s1.status_id 
    AND e.stress_status = s2.status_id 

Answer 3

剛剛加入兩次，狀態表

From 
     Entry e 
    Inner join status ds 
    On e. design_status_id = ds.status_id 
    Inner join status ss 
    On e.stress_status_id = ss.status_id 

Answer 4

幾種方法，首先是最有效的。

 
SELECT 
    e.entry_id 
    , MAX(CASE WHEN e.design_status = s.status_id THEN s.status_descrip END) AS design_status_descrip 
    , MAX(CASE WHEN e.stress_status = s.status_id THEN s.status_descrip END) AS stress_status_descrip 
FROM 
    dbo.[Entry] e 
LEFT OUTER JOIN 
    dbo.[Status] s 
ON s.status_id = e.design_status 
OR s.status_id = e.stress_status 
GROUP BY 
    entry_id
 

SELECT e.entry_id , ds.status_descrip AS design_status_descrip , ss.status_descrip AS stress_status_descrip FROM dbo.[Entry] e LEFT OUTER JOIN dbo.[status] ds ON ds.status_id = e.design_status LEFT OUTER JOIN dbo.[status] ss ON ss.status_id = e.stress_status 

Answer 5

我注意到你在你的數據NULL的，在這種情況下，忽略使用INNER JOIN因爲這將有效地過濾掉任何行，在其中任何一列空了所有的答案。而是使用左連接。

SELECT 
    e.entry_id, 
    ds.status_description, 
    ss.ststua_description 
FROM entry e 
LEFT JOIN status ds 
    ON e.design_status = ds.status_id 
LEFT JOIN status ss 
    ON e.stress_status = ss.status_id