Question

我需要一个小查询的帮助。

表A： - 状态及其内容如下。

 status_id      status_descrip 
        1          held 
        2          release 
        3          WIP

表B： - 条目是另一个有30个字段的表。其中2个字段指的是表A->状态表。为简单起见，我正在跳过其他字段并仅记下与状态相关的字段。

 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

我无法将Entry的结构更改为分为2个表，一个作为design_status，另一个作为stress_status。

现在我希望条目表中的条目将状态替换为其描述。所以输出将是

   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

提前致谢！

编辑： -

使用条目编辑问题。

谢谢您的所有回复！

最终为我工作的查询是，

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

请告诉我，如果我可以改进此查询。

Answer 1

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 2

只需加入两次状态表

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 3

最简单的方法是两次加入状态表。假设架构中的design_status和stress_status列具有适当的约束，我使用了INNER JOIN。编辑了变更的要求。

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 4

一些方法，首先是效率最高的。

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

我注意到您的数据中包含NULL，在这种情况下，使用INNER JOIN忽略所有答案，因为这将有效地过滤掉任一列中为空的任何行。而是使用左连接。

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

查询查询

5 个答案: