查詢來獲取這是大於零ANS最低值不爲空

Question

我有一個查詢：

SELECT 
    taskDeadline, 
    subtasksDeadline, 
    REPLACE(
     LEAST(
      COALESCE(t.deadline, 2147483647), 
      COALESCE(sub.deadline, 2147483647) 
     ), 2147483647, NULL 
    ) AS Deadline 
FROM 
    tasks t 
    LEFT OUTER JOIN subtasks sub ON sub.task_id = t.id 

這產生的結果是這樣的：

taskDeadline | subtasksDeadline | Deadline 
1338501600 | 1333058400  | 1333058400 
1334268000 | NULL    | 1334268000 
NULL   | 1328050800  | 1328050800 
NULL   | NULL    | NULL 
1353798000 | 0    | 0 
0   | 1353798000  | 0 

我幾乎沒有。我用2147483647的數據類型（mysql的INT）的最大值，我仍然有唯一的問題是，如果我有兩個值，其中一個是0，我想其他的價值。我花了一些時間，但無法到達那裏。有人可以闡明這一點嗎？

Answer 1

或者只是添加NULLIF到您現有的COALESCE -

SELECT 
    taskDeadline, 
    subtasksDeadline, 
    NULLIF(
     LEAST(
      COALESCE(NULLIF(t.deadline, 0), 2147483647), 
      COALESCE(NULLIF(sub.deadline, 0), 2147483647) 
     ), 2147483647 
    ) AS Deadline 
FROM 
    tasks t 
    LEFT OUTER JOIN subtasks sub ON sub.task_id = t.id 

Answer 2

如果我理解正確，如果零爲最小值，則不需要t.deadline和sub.deadline的零值。所以你可以將0轉換爲NULL，這將被擠出COALESCE

SELECT 
    taskDeadline, 
    subtasksDeadline, 
    REPLACE(
     LEAST(
      COALESCE(IF(t.deadline = 0, NULL, t.deadline), 2147483647), 
      COALESCE(IF(sub.deadline = 0, NULL, sub.deadline), 2147483647) 
     ), 2147483647, NULL 
    ) AS Deadline 
FROM 
    tasks t 
    LEFT OUTER JOIN subtasks sub ON sub.task_id = t.id 

Answer 3

爲什麼不使用case語句？

SELECT 
    taskDeadline, 
    subtasksDeadline, 
    CASE 
     WHEN t.deadline IS NULL AND sub.deadline IS NULL THEN NULL 
     WHEN t.deadline IS NULL THEN sub.deadline 
     WHEN sub.deadline IS NULL THEN t.deadline 
     WHEN t.deadline > sub.deadline THEN sub.deadline 
     WHEN sub.deadline > t.deadline THEN t.deadline 
     WHEN sub.deadline = t.deadline THEN sub.deadline -- or this could be t.deadline 
    END AS Deadline 
FROM 
    tasks t 
    LEFT OUTER JOIN subtasks sub 
     ON sub.task_id = t.id 

Answer 4

嘗試使用此查詢 -

SELECT 
    taskDeadline, 
    subtasksDeadline, 
    LEAST(
     IF(t.deadline = 0 OR t.deadline IS NULL, sub.deadline, t.deadline), 
     IF(sub.deadline = 0 OR sub.deadline IS NULL, t.deadline, sub.deadline) 
    ) AS Deadline 
FROM 
    tasks t 
    LEFT OUTER JOIN subtasks sub ON sub.task_id = t.id