MySQL - 如何進行自聯接以返回重疊的日期范圍？

Question

我有一個組織內成員持有的歷史職位任期表（tbl_tenue）。 每個職位一次只能由一個人持有，但是一個人可以順序或同時持有多個職位。 我想通過依次獲取每個位置任期記錄然后將其與表中的每個其他記錄進行比較來檢查該表的完整性，以查找與同一位置的其他任期的（錯誤的）重疊。

我編寫了一個工作查詢（下面），它在傳遞test_tenure_id，position_id以及特定任期的開始和結束日期時返回重疊的詳細信息（見下文）。 此查詢返回tenure_id，member_id，member_sn，date_started，date_ended和重疊原因。

任何人都可以幫助我使用sql來對同一個tbl_tenue表運行此查詢，每次從tbl_tenue中的一行傳遞數據，這樣我就可以測試每個記錄與其他每個記錄重疊（當然除了它自己）並返回數據從記錄及其所有重疊？

（我意識到，如果我能做到這一點，那么我應該能夠避免通過使用連接將tenure_id傳遞給WHERE子句，並且還避免使用連接傳遞日期但我無法看到如何在那一刻，所以任何幫助都會很好）

下面的查詢使用以下表格，針對此問題進行了簡化

TABLE tbl_member 
  ( member_id INT AUTO_INCREMENT, -- pk
    member_sn` varchar(50) , --surname
    <other stuff>
  )

TABLE tbl_tenure
  (tenure_id INT AUTO_INCREMENT, -- pk
   member_id INT -- fk to tbl_member
   position_id -- fk to table of position titles
   date_started DATE
   date_ended DATE -- will be NULL if still in post
  )


  -- test data for query
  SET @the_test_tenure_start_date = '2016-05-13' ;
  SET @the_test_tenure_end_date = '2016-10-05';
  SET @the_test_position_id = 18; 
  SET @the_test_tenue_id = 122;

-- the query to return overlaps with data from a given tenure record  
SELECT
   tbl_tenure.tenure_id,
   tbl_tenure.member_id,
   tbl_member.member_sn,
   tbl_tenure.date_started,
   tbl_tenure.date_ended,
   CASE
      WHEN @the_test_tenure_end_date <= IFNULL(date_ended, CURDATE())  -- test end date <= existing end date
      AND @the_test_tenure_start_date >= date_started   -- test start date >= existing start date
      THEN 'Test dates fall completely inside an existing tenure'

      WHEN @the_test_tenure_end_date >= IFNULL(date_ended, CURDATE())   -- test end date >= existing end date
      AND @the_test_tenure_start_date <= date_started   -- test start date <= existing start date
      THEN 'An existing tenure falls completely inside test dates'

      WHEN @the_test_tenure_start_date >= date_started   -- test start date >= existing start date
      AND @the_test_tenure_start_date <= IFNULL(date_ended, CURDATE())   -- test start date <= existing end date
      THEN 'Test start date overlaps with an existing tenure'

      WHEN @the_test_tenure_end_date >= date_started   -- test end date >= existing start date
      AND @the_test_tenure_end_date <= IFNULL(date_ended, CURDATE())   -- test end date <= existing end date
      THEN 'Test end date overlaps with an existing tenure'
   END AS reason

FROM
   tbl_tenure
   INNER JOIN tbl_member
      ON tbl_tenure.member_id = tbl_member.member_id

WHERE ( -- there is an overlap (see qry 2.2 http://salman-w.blogspot.co.uk/2012/06/sql-query-overlapping-date-ranges.html
          @the_test_tenure_end_date >= date_started)    
          AND 
      IFNULL(date_ended, CURDATE()) >= @the_test_tenure_start_date
      )   
   AND tbl_tenure.position_id = @the_test_position_id   -- position to be tested
   AND  tbl_tenure.tenure_id <> @the_test_tenue_id    -- don't look at the test tenure record
ORDER BY tbl_tenure.date_started ASC;

為了澄清這個問題，我正在尋找的輸出是這樣的，請注意tenure_id 132，其中一個成員被記錄為與自己一起過度

tenure_id   | member_id     | position_id   | start_date | end_date   | overlapping_member_id | overlapping_tenure_id | overlapping_start_date |overlapping_end_date | overlap_reason
   123      |      2        |      6        | 2016-02-01 | 2016 02-01 |       7               |       456             |     2016-01-05         |   2016-01-10         |'Test start date overlaps with an existing tenure'
   125      |      2        |      8        | 2016-02-01 | 2016 03-01 |       8               |       459             |     2016-01-0          |   2016-02-01         |'Test end date overlaps with an existing tenure'
   129      |      4        |      7        | 2016-03-10 | 2016 04-01 |       6               |       501             |     2016-03-2          |   2016-03-25         |'An existing tenure falls completely inside test dates'
   132      |      4        |      7        | 2016-01-01 | 2016 04-01 |       4               |       505             |     2016-03-01         |   2016-04-01         |'Test end date overlaps with an existing tenure'
   135      |      9        |      3        | 2016-05-01 | 2016 07-01 |       9               |       520             |     2016-04-0          |   2016-08-01         |'Test dates fall completely inside an existing tenure'

Answer 1

花了一天的時間在跑步機上跑步並且在跑步機上跑步時我相信我有答案。 我在這里張貼它是為了別人的利益。 我將使用tbl_member的連接移動到子查詢中，並且為了完整性，包括另一個子查詢以從第三個表tbl_position獲得位置的實際標題，如下所示。 （看不到用連接替換子查詢的方法，但這無關緊要。）

TABLE tbl_positions
   (
   position_id INT AUTO_INCREMENT, -- pk
   position VARCHAR(100), -- title of position
   <other stuff>
   )

我想出的代碼在下面似乎正常工作，並顯示所有重疊的詳細信息，其中包括誰，何時以及為何重疊。

諷刺的是，例如，如果弗雷德被證明與吉姆的現有記錄重疊為總統，而弗雷德的任期完全包含吉姆的任期，那么吉姆作為總統的職位也顯示與弗雷德現有的任期記錄重疊，原因是鑒於弗雷德完全被吉姆所包圍。 即我得到重疊的兩面。

如果有一種快速的方法來獲得“單向”重疊，那么通過各種方式發布更好的答案。

我的答案

SELECT
   base_tenure.position_id     AS base_tenure_id,
   base_tenure.member_id     AS base_member_id,
   (SELECT member_sn FROM tbl_member WHERE tbl_member.member_id = base_tenure.member_id)     AS base_sn,
   (SELECT tbl_positions.position FROM tbl_positions WHERE tbl_positions.position_id = base_tenure.position_id ) AS POSITION,
   base_tenure.date_started  AS base_date_started,
   base_tenure.date_ended    AS base_date_ended,

   overlap_tenure.position_id  AS overlap_tenure_id,
   overlap_tenure.member_id AS overlap_member_id,
   (SELECT member_sn FROM tbl_member WHERE tbl_member.member_id = overlap_tenure.member_id)     AS overlap_sn,
   overlap_tenure.date_started AS overlap_date_started,
   overlap_tenure.date_ended   AS overlap_date_ended,  

   CASE
      WHEN base_tenure.date_ended <= IFNULL(overlap_tenure.date_ended, CURDATE())-- test end date <= existing end date
      AND base_tenure.date_started >= overlap_tenure.date_started  -- test start date >= existing start date
      THEN 'tbl_member dates fall completely inside an existing tenue'

      WHEN base_tenure.date_ended >= IFNULL(overlap_tenure.date_ended, CURDATE()) -- test end date >= existing end date
      AND base_tenure.date_started <=  overlap_tenure.date_started -- test start date <= existing start date
      THEN 'An existing tenue falls completely inside tbl_member dates'

      WHEN base_tenure.date_started >= overlap_tenure.date_started  -- test start date >= existing start date
      AND base_tenure.date_started <= IFNULL( overlap_tenure.date_ended , CURDATE()) -- test start date <= existing end date
      THEN 'tbl_member start date overlaps with an existing tenue'

      WHEN base_tenure.date_ended >= overlap_tenure.date_started  -- test end date >= existing start date
      AND base_tenure.date_ended <= IFNULL( overlap_tenure.date_ended , CURDATE())-- test end date <= existing end date
      THEN 'tbl_member end date overlaps with an existing tenue'
   END AS reason

FROM -- a self join on tbl_tenure
   tbl_tenure AS base_tenure,
   tbl_tenure AS overlap_tenure

WHERE (-- there is an overlap (see qry 2.2 http://salman-w.blogspot.co.uk/2012/06/sql-query-overlapping-date-ranges.html
           base_tenure.date_ended  >= overlap_tenure.date_started -- test end date >= existing start date
          AND 
          IFNULL(overlap_tenure.date_ended, CURDATE()) >= base_tenure.date_started 
          )

   AND 
      base_tenure.club_function_id = overlap_tenure.club_function_id -- positions are the same for both members

   AND  
      base_tenure.position_id <> overlap_tenure.position_id --  don't compare the base record with itself as they are identical and will always overlap 

 ORDER BY
       (SELECT member_sn FROM tbl_member WHERE tbl_member.member_id = base_tenure.member_id) ,
       base_tenure.date_started ;