組合查詢返回不同的結果

Question

我從兩個不同的查詢創建的查詢的結果不會返回相同的結果。

查詢

SELECT 
c.fullname Course, 
u.firstname First, 
u.lastname Last, 
u.id ID, 
u.institution Company 

FROM (mdl_scorm_scoes_track AS st) 
JOIN mdl_user AS u ON st.userid=u.id 
JOIN mdl_scorm AS sc ON sc.id=st.scormid 
JOIN mdl_course AS c ON c.id=sc.course 
Join mdl_user_enrolments AS uenr ON uenr.userid=u.id 
Join mdl_enrol AS enr ON enr.id=uenr.enrolid 

WHERE (
(st.value='incomplete' OR st.value='not attempted') 
AND DATEDIFF(NOW(), FROM_UNIXTIME(uenr.timecreated)>60) 
ORDER BY c.fullname, u.lastname,u.firstname, u.id 

查詢乙

SELECT 
c.fullname AS Course, 
u.firstname AS Firstname, 
u.lastname AS Lastname, 
u.id AS ID, 
u.institution AS Company, 

IF (u.lastaccess = 0,'never', 
DATE_FORMAT(FROM_UNIXTIME(u.lastaccess),'%Y-%m-%d')) AS dLastAccess 

,(SELECT DATE_FORMAT(FROM_UNIXTIME(timeaccess),'%Y-%m-%d') FROM mdl_user_lastaccess WHERE userid=u.id AND courseid=c.id) AS CourseLastAccess 
FROM mdl_user_enrolments AS ue 
JOIN mdl_enrol AS e ON e.id = ue.enrolid 
JOIN mdl_course AS c ON c.id = e.courseid 
JOIN mdl_user AS u ON u.id = ue.userid 
LEFT JOIN mdl_user_lastaccess AS ul ON ul.userid = u.id 
WHERE ul.timeaccess IS NULL AND (DATEDIFF(NOW(), FROM_UNIXTIME(ue.timecreated))>60) 
ORDER BY u.id, c.fullname 

我已經它們合併成查詢Ç

SELECT 
c.fullname AS Course, 
u.firstname AS Firstname, 
u.lastname AS Lastname, 
u.id AS IDNumber, 
u.institution AS Institution, 

IF (u.lastaccess = 0,'never', 
DATE_FORMAT(FROM_UNIXTIME(u.lastaccess),'%Y-%m-%d')) AS dLastAccess 

,(SELECT DATE_FORMAT(FROM_UNIXTIME(timeaccess),'%Y-%m-%d') FROM mdl_user_lastaccess WHERE userid=u.id AND courseid=c.id) AS CourseLastAccess 


FROM mdl_user_enrolments AS ue 
JOIN mdl_enrol AS e ON e.id = ue.enrolid 
JOIN mdl_course AS c ON c.id = e.courseid 
JOIN mdl_user AS u ON u.id = ue.userid 
LEFT JOIN mdl_user_lastaccess AS ul ON ul.userid = u.id 
WHERE (ul.timeaccess IS NULL OR ue.userid IN 
(SELECT u.id 
FROM (mdl_scorm_scoes_track AS st) 
JOIN mdl_scorm AS sc ON sc.id=st.scormid 

WHERE c.id=sc.course AND st.userid=u.id AND (st.value='incomplete' OR st.value='not attempted') 
) 
)AND (DATEDIFF(NOW(), FROM_UNIXTIME(ue.timecreated))>60) 
ORDER BY c.fullname, u.lastname,u.firstname 

我還沒有發現在我的邏輯是在查詢C.查詢不正確C會添加A或B未找到的錯誤記錄，並在幾個情況下複製條目。

我想了解一下我的邏輯組合2的方式走向歧途。

我在這篇文章中修正了逗號，實際的查詢確實有這些逗號。

我的意圖是列出所有已登記進入課程但在給定時間範圍內的用戶，尚未登錄系統，訪問課程並最終沒有完成課程中的活動。

所以我要尋找的邏輯是： 如果60天之內用戶沒有登錄 - 顯示名稱 如果登錄，但一直沒有在60天內訪問過課程 - 顯示名稱 如果登錄並訪問查詢A確實列出所有在60天內開始活動但尚未完成的用戶 查詢B確實列出了所有未登錄或訪問課程的用戶60天

在試圖結合2個查詢來滿足所有3個條件離子是我遇到問題的地方。我第一次嘗試了一個聯盟，但無法實現它的工作。

Answer 1

在這兩個查詢中，您並未從同一個世界中進行選擇。查詢A有6個表格可供選擇，而查詢B有5個表格（它缺少mdl_scorm表格），而你的查詢C具有查詢B具有的5個表格。所以現在你的查詢A的範圍已經改變了。該額外的表可能已經消除了現在出現在查詢C中的選擇A的行。

我會檢查查詢A，查詢中缺少mdl_scorm表，並且您可能具有不同的結果大小。

把它想象成

從表中選擇COLUMNS where FILTERS; TABLES（數據的宇宙）需要在兩個查詢中都相同，才能加入COLUMNS和FILTERS（擴展選擇和限制結果）