单个 SQL 查询出错

Question

我正在尝试为我的数据库编写一个 SQL 查询，该查询将检索所有特定用户事件。如果它们被标记为重复出现，我希望它们在开始日期后的 52 周内每周出现一次。有没有更好的方法来做到这一点？我当前的代码看起来很笨重。

我的表格结构如下：

   event (
    event_id INT NOT NULL AUTO_INCREMENT, (PK)
    title VARCHAR(80) NOT NULL,
    description VARCHAR(200),
    event_start DATETIME,
    event_end DATETIME,
    group_id INT NOT NULL,
    recurring BOOLEAN
);

   Users{
    UserID (PK)
    Username
   }

   Groups{
    GroupID (PK)
    GroupName
   }

   Membership{
    UserID (FK)
    GroupID (FK)
   }

这是我目前的查询，目前无法使用，有人可以帮我吗？

 var result = db.Query(
            @"SELECT e.event_id, e.title, e.description, e.event_start, e.event_end, e.group_id, e.recurring
            FROM   event e
            JOIN   Membership m ON m.GroupID = e.group_id
            WHERE  e.recurring
            AND    m.UserID = ?
            AND    e.event_start >= ?
            AND    e.event_end <= ?
            UNION ALL
            SELECT e.event_id, e.title, e.description, DATEADD(week, w.weeks, e.event_start),
                   DATEADD(week, w.weeks, e.event_end), e.group_id, e.recurring
            FROM   event e
            JOIN   Membership m ON m.GroupID = e.group_id,
            (SELECT row_number() OVER (ORDER BY Object_ID) AS weeks
                    FROM SYS.OBJECTS) AS w
            WHERE  NOT e.recurring
            AND    m.user_id = ?
            AND    e.event_start >= ?
            AND    e.event_end <= ?", username, start, end, username, start, end
        );

谁能帮我调整我的代码，使其选择所有不重复的事件，并在 52 周内同时选择重复事件？

Answer 1

可能是这样的：

SELECT e.event_id, e.title, e.description, e.start_time, e.end_time
     , e.group_id, e.recurring
FROM   Events e
JOIN   Membership m ON m.groupid = e.group_id
WHERE  e.recurring = 0 
AND    m.user_id = ?
AND    e.start_time >= ?
AND    e.end_time <= ?

UNION ALL
SELECT e.event_ID, e.title, e.description
      ,DATEADD(week, w.weeks, e.start_time) -- AS event_start
      ,DATEADD(week, w.weeks, e.end_time)   -- AS event_end
      ,e.group_id, e.recurring
FROM   Events e
JOIN   Membership m ON m.groupid = e.group_id
      ,(SELECT row_number() OVER (ORDER BY Object_ID) AS weeks
        FROM SYS.OBJECTS) AS w
WHERE  e.recurring = 1
AND    m.user_id = ?
AND    e.start_time >= ?
AND    e.end_time <= ?

• 使用UNION ALL 而不是UNION。

• event_start 和 event_end 而不是 start_time 和 end_time (??) 我改了。

• 一开始我也错过了：user_id 在表 Membership 中，所以如果你想在 WHERE 子句中使用它，你需要 JOIN 在里面。外键列似乎是group_id / groupid。 （我会统一拼写！）

• 您在查询的第一部分中有 SELECT *。最好在这样的查询中拼出列名，否则以后对基础表的更改会以令人惊讶的方式破坏它。

• 我的初稿有一个辅助函数 generate_series() 从 here 生成数字 1-52 的集合，但您原来的解决方案更好，所以我恢复了这个更改。

Answer 2

试试这个。您在 SQL 中使用了 event_start 和 event_stop，但它们没有在表事件中定义。您唯一混淆的是 start_time = @CurrentTime。我不认为你的代码很笨重。 UNION ALL 比 UNION 执行得更好（UNION 的工作方式类似于 DISTINCT：首先 ORDER BY 然后删除重复项）。

DROP TABLE #Events
CREATE TABLE #Events (
  event_id  INT NOT NULL,
  title VARCHAR(80) NOT NULL,
  description   VARCHAR(200),
  start_time    DATETIME,
  end_time  DATETIME,
  group_id  INT NOT NULL,
  recurring bit
);

INSERT INTO #Events(event_id, title, description, start_time, end_time, group_id, recurring) VALUES
(1, 'meeting1', 'meeting1', '20000101', '20000102', 1, 0),
(2, 'meeting2', 'meeting2', '20120309', '20120310', 1, 0),
(3, 'meeting3', 'meeting3', '20120311', '20120312', 1, 0),
(10, 'meeting10', 'meeting10', '20000101', '20000102', 1, 1),
(20, 'meeting20', 'meeting20', '20120309', '20120310', 1, 1),
(30, 'meeting30', 'meeting30', '20120311', '20120312', 1, 1)

DECLARE @CurrentTime DATETIME
SET @CurrentTime = GETDATE()

SELECT event_id, 
    title,
    description, 
    start_time, 
    end_time, 
    group_id, 
    recurring
FROM #Events 
WHERE recurring = 0 AND 
--  user_id = ? AND 
  start_time <= @CurrentTime AND 
  end_time >= @CurrentTime

UNION ALL

SELECT event_ID, 
  title, 
  description, 
  DATEADD(WEEK, Interval, start_time) [event_start], 
  DATEADD(WEEK, Interval, end_time) [event_end], 
  group_id, 
  recurring
FROM #Events,
  (SELECT ROW_NUMBER() OVER(ORDER BY Object_ID) [Interval]
  FROM SYS.OBJECTS) as T 
WHERE recurring = 1 AND 
  Interval <= 52 AND 
--  user_id = ? AND 
  start_time <= @CurrentTime AND 
  end_time >= @CurrentTime
;