在同一個表中獲取行

想象一下，我有兩個記錄（t1和t2）。我想獲取沒有t1.start_hour BETWEEN t2.start_hour和t2.finish_hour的行。我基本上只想得到與另一個小時沒有衝突的事件。

這是表：

create_table "occurrences", :force => true do |t| 
    t.string "start_hour" 
    t.string "finish_hour" 
    t.date  "start_date" 
    t.date  "finish_date" 
    t.datetime "created_at", :null => false 
    t.datetime "updated_at", :null => false 
    t.integer "activity_id" 
    end

這是SQL查詢我想出迄今：

Occurrence.find_by_sql("SELECT * FROM occurrences t1 INNER JOIN occurrences t2 ON (t1.start_hour NOT BETWEEN t2.start_hour and t2.finish_hour)")

它讓我重複的結果。我無法刪除它們並得到正確的答案。

感謝您的幫助提前。

例

INPUT

#<Occurrence id: 1, start_hour: "19:00", finish_hour: "20:20", start_date: "2012-05-30", finish_date: "2012-05-30", created_at: "2012-05-30 09:58:19", updated_at: "2012-05-30 09:58:19", activity_id: 1>, 

#<Occurrence id: 2, start_hour: "19:30", finish_hour: "20:10", start_date: "2012-05-30", finish_date: "2012-05-30", created_at: "2012-05-30 09:58:19", updated_at: "2012-05-30 09:58:19", activity_id: 2>, 

#<Occurrence id: 3, start_hour: "22:00", finish_hour: "23:20", start_date: "2012-05-30", finish_date: "2012-05-30", created_at: "2012-05-30 09:58:20", updated_at: "2012-05-30 09:58:20", activity_id: 3>

OUTPUT

#<Occurrence id: 1, start_hour: "19:00", finish_hour: "20:20", start_date: "2012-05-30", finish_date: "2012-05-30", created_at: "2012-05-30 09:58:19", updated_at: "2012-05-30 09:58:19", activity_id: 1>, 

#<Occurrence id: 3, start_hour: "22:00", finish_hour: "23:20", start_date: "2012-05-30", finish_date: "2012-05-30", created_at: "2012-05-30 09:58:20", updated_at: "2012-05-30 09:58:20", activity_id: 3>

與START_HOUR記錄= 19:30不輸出因爲是19:00和另一個的20:20之間。

編輯：

我得到了解決：

Occurrence.find_by_sql("SELECT start_hour FROM occurrences WHERE start_hour NOT IN (SELECT t2.start_hour FROM occurrences t1 INNER JOIN occurrences t2 ON ((t1.activity_id <> t2.activity_id AND t2.start_hour BETWEEN t1.start_hour and t1.finish_hour)))")

感謝您的幫助

來源

2012-05-30 António Silva

請張貼一些示例數據和預期的輸出。 – Quassnoi

我無法理解你在這裏實現的目標。如果你能提供更多關於你正在試圖解決的現實世界問題的細節，那會更好。 – rubish

讓我們假設有3條記錄表。（我正在整數代替DATATIME因爲這將是更容易）

id  start end 
    1  1  3 
    2  4  5 
    3  7  9

當我將嘗試找到行的人開始不是起點和終點之間，比ID = 1兩第一行會真實並且會產生結果。類似地，對於id = 2（start = 4）的行，兩行都有資格（使第三行在結果中出現兩次）第三行也會發生同樣的情況，最後會出現六行。

它不是很清楚你想在這裏實現什麼，但把明顯將刪除重複。

編輯：你可能會考慮把內部連接放在開始和結束日期。

來源

2012-05-30 10:01:06

沒有（從內存中）需要exlude記錄本身測試 - > t1.activity_id <> t2.activity_id 左加入，否則將無法獲得好的那裏沒有右側

需要對此進行測試：對

SELECT * FROM occurrences t1 
left JOIN occurrences t2 
ON (t1.activity_id <> t2.activity_id and t1.start_hour BETWEEN t2.start_hour and t2.finish_hour) 
where t2.activity_id is null

來源

2012-05-30 10:13:28

結果是所有字段都爲零值的兩條記錄。編輯：號碼記錄是正確的。 –

在同一個表中獲取行

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