mysql如何顯示，也不匹配where子句

Question

我有這個疑問行：

SELECT `y78f2_students`.`firstname` , `y78f2_students`.`lastName` , `y78f2_students`.`student_id`,`y78f2_attendance`.`is_present`, `y78f2_attendance`.`note`, `y78f2_attendance`.`thedate` 
FROM `y78f2_students` 
INNER JOIN `y78f2_enrolls` ON `y78f2_enrolls`.`student_id` = `y78f2_students`.`student_id` 
INNER JOIN `y78f2_attendance` ON `y78f2_attendance`.`student_id` = `y78f2_students`.`student_id` 
WHERE `y78f2_enrolls`.`term` = 'Term 2 2016' 
AND `y78f2_enrolls`.`crn_class` = 'Math1R1' 
and `y78f2_attendance`.`thedate` = '2016-01-24' 
ORDER BY thedate desc 

此查詢僅返回其中的日期爲「2016年1月24日」的行。目前這只是一行：http://i.imgur.com/jRTBqQ0.png

我需要顯示所有行，其中term ='Term 2 2016'和crn_class` ='Math1R1'以及日期尚未設置的位置。換句話說，我想向班上的所有學生展示，如果還沒有爲這些學生設置日期，它將顯示爲空。 這就是我想要的：http://i.imgur.com/jmsuSF5.png

所以總而言之，我需要顯示哪些行符合條款，哪些日期將爲空或不存在。 如何編寫此查詢？

Answer 1

嘗試從查詢的末尾移動與連接表相關的條件，直到每個連接的表各自的ON子句。另外，如果您想要返回y78f2_attendance表中尚無行存在的記錄，則該表應該是LEFT OUTER已加入，而不是INNER已加入。

SELECT `y78f2_students`.`firstname` , `y78f2_students`.`lastName`, 
    `y78f2_students`.`student_id`,`y78f2_attendance`.`is_present`, 
    `y78f2_attendance`.`note`, `y78f2_attendance`.`thedate` 
FROM `y78f2_students` 
INNER JOIN `y78f2_enrolls` ON 
    `y78f2_enrolls`.`student_id` = `y78f2_students`.`student_id` 
    AND `y78f2_enrolls`.`crn_class` = 'Math1R1' 
LEFT OUTER JOIN `y78f2_attendance` ON 
    `y78f2_attendance`.`student_id` = `y78f2_students`.`student_id` 
    AND (`y78f2_attendance`.`thedate` IS NULL OR `y78f2_attendance`.`thedate` = '2016-01-24') 
WHERE `y78f2_enrolls`.`term` = 'Term 2 2016' 
ORDER BY thedate desc