Question

我有此代码

$q = $conn->query("SELECT facultydetails.F_NAME,Paper_title from faculty inner join facultydetails on faculty.Fac_ID = facultydetails.Fac_ID where (paper_path = 'NULL' OR paper_path = '') and  (certificate_path = 'NULL' OR certificate_path = '') and (report_path = 'NULL' OR report_path = '') " );

现在我需要添加一个条件，用户将提供该ID，并且只有该ID相关的内容才可以被我使用，

$q = $conn->query("SELECT facultydetails.F_NAME,Paper_title from faculty where facultydetails.Fac_ID='$FacID' inner join facultydetails on faculty.Fac_ID = facultydetails.Fac_ID where (paper_path = 'NULL' OR paper_path = '') and  (certificate_path = 'NULL' OR certificate_path = '') and (report_path = 'NULL' OR report_path = '') " );

使用php

Answer 1

不，您不能在内部联接之前添加where子句。

内部联接的语法如下：

SELECT column_list
FROM t1
INNER JOIN t2 ON join_condition1
INNER JOIN t3 ON join_condition2
...
WHERE where_conditions;

Answer 2

SELECT facultydetails.F_NAME,Paper_title 
from faculty 
inner join facultydetails on faculty.Fac_ID = facultydetails.Fac_ID 
where facultydetails.Fac_ID='$FacID' 
AND (paper_path = 'NULL' OR paper_path = '') and  (certificate_path = 'NULL' OR certificate_path = '') and (report_path = 'NULL' OR report_path = '')

Answer 3

您不能在内部联接之前添加where，但是您可以将条件添加到on子句中，例如：

"SELECT facultydetails.F_NAME,Paper_title ".
"from faculty ".
"inner join facultydetails ".
"on (facultydetails.Fac_ID='$FacID') and (faculty.Fac_ID = facultydetails.Fac_ID) ".
"where (paper_path = 'NULL' OR paper_path = '') and  (certificate_path = 'NULL' OR certificate_path = '') and (report_path = 'NULL' OR report_path = '') "

或者您可以预过滤您的教职员工表，例如：

"SELECT facultydetails.F_NAME,Paper_title ".
"from (select * from faculty where (facultydetails.Fac_ID='$FacID')) f ".
"inner join facultydetails ".
"on f.Fac_ID = facultydetails.Fac_ID ".
"where (paper_path = 'NULL' OR paper_path = '') and  (certificate_path = 'NULL' OR certificate_path = '') and (report_path = 'NULL' OR report_path = '') "

编辑：

在SQL中，在单个查询中其他部分位于代码“上方”或“下方”的情况下，将不能保证在此代码之前先执行该代码。

我可以在内部联接子句之前包含where子句吗

3 个答案: