MySQL-通过匹配引用从多个表中获取数据

Question

我尝试使用join查询从不同的表中获取数据。但即使有数据，它也不会返回任何结果。

“学生主表”包含有关该学生的详细信息。学生的学籍号码是本表的主键。将滚动号添加到所有结果表(即first_term_results、second_term_results等)中以供参考。

因此，为了获取学生的详细信息，他的第一学期和第二学期的成绩，我使用以下查询，没有给出预期的结果。我正在尝试获取与roll_no匹配的细节。

SELECT a.*, b .*,c.*
FROM student_master AS a
INNER JOIN first_term_results AS b
INNER JOIN second_term_results AS c
ON a.roll_no = b.roll_no = c.roll_no
WHERE a.roll_no = '53'
AND b.roll_no='53'
AND c.roll_no = '53'

有人能帮我纠正这个查询，得到我期待的结果?.Also，请告诉我，如果我是不清楚的。我可以解释。

提前谢谢。

Answer 1

在将查询格式化为可读的内容之后，我得到以下内容

SELECT a.*, b .*,c.* 
FROM   student_master AS a 
  INNER JOIN first_term_results AS b 
  INNER JOIN second_term_results AS c ON a.roll_no = b.roll_no = c.roll_no 
WHERE   a.roll_no = '53' 
AND     b.roll_no='53'
AND     c.roll_no = '53'

对我来说有点奇怪，我会去做这样的事情

SELECT a.*, b .*,c.* 
FROM   student_master AS a 
  INNER JOIN first_term_results AS b on a.roll_no = b.roll_no 
  INNER JOIN second_term_results AS c ON a.roll_no = c.roll_no 
WHERE   a.roll_no = '53' 

Answer 2

将查询修改为

SELECT a.*, b.*,c.*
FROM student_master AS a
INNER JOIN first_term_results AS b ON a.roll_no = b.roll_no
INNER JOIN second_term_results AS c ON a.roll_no = c.roll_no
WHERE a.roll_no = '53'

Answer 3

这应该符合你的愿望：

SELECT a.*, b .*,c.*
FROM student_master AS a
LEFT JOIN first_term_results AS b ON(a.roll_no = b.roll_no)
LEFT JOIN second_term_results AS c ON( a.roll_no = c.roll_no)
WHERE a.roll_no = '53'

您是否检查了驱动程序返回的错误？