Php 使用不同的where子句连接2个表

我的数据库中有2个表

1.管理商店\u考试 列是 考试名称，A数量，数学问题，数学A，数学b，数学c，数学d，A答案

2.学生历史 列是 考试名称、学生ID、学生数量、学生人数、学生人数

现在我想用不同的WHERE子句连接exam\u name列上的这两个表

$sql="SELECT * FROM admin_store_exam WHERE exam_name='$en'";

$sql="SELECT * FROM student_ans_history WHERE exam_name='$en' AND S_ID='$session_contact'";

下面是带有WHERE子句的两个不同查询

$sql="SELECT * FROM admin_store_exam WHERE exam_name='$en'";

$sql="SELECT * FROM student_ans_history WHERE exam_name='$en' AND S_ID='$session_contact'";

加入这两张桌子后，我得到了这些

$sql="
SELECT admin_store_exam.A_QNum
     , admin_store_exam.math_ques
     , admin_store_exam.math_a
     , admin_store_exam.math_b
     , admin_store_exam.math_c
     , admin_store_exam.math_d
     , admin_store_exam.A_Ans
     , student_ans_history.S_Ans
     , student_ans_history.S_Noans 
  FROM admin_store_exam 
 WHERE admin_store_exam.exam_name = '$en' 
  JOIN student_ans_history 
 WHERE student_ans_history.exam_name = '$en' 
   AND S_ID = '$session_contact' 
    ON admin_store_exam.exam_name = student_ans_history.exam_name
 ";

但不幸的是，我不会得到任何结果。

---

我对sql不是很熟悉，因此无法理解我在哪里犯了错误。谁能帮我解决这个问题。谢谢。

您可以使用子查询。考虑下面的例子：

SELECT A.* FROM
(SELECT * FROM admin_store_exam WHERE exam_name='AB') AS A
INNER JOIN
(SELECT * FROM student_ans_history WHERE exam_name='AB' AND S_ID='23344') AS B
ON A.exam_name = B.exam_name

您可以像这样加入它：

$sql="SELECT admin_store_exam.A_QNum
 , admin_store_exam.math_ques
 , admin_store_exam.math_a
 , admin_store_exam.math_b
 , admin_store_exam.math_c
 , admin_store_exam.math_d
 , admin_store_exam.A_Ans
 , CONCAT(S_Ans,S_Noans) AS S_Ans
  FROM admin_store_exam 
 INNER 
  JOIN student_ans_history 
    ON admin_store_exam.exam_name = student_ans_history.exam_name 
        AND admin_store_exam.A_QNum = student_ans_history.S_QNum
 WHERE admin_store_exam.exam_name = '$en' 
   AND student_ans_history.S_ID = '$session_contact'
    GROUP BY admin_store_exam.exam_name, admin_store_exam.A_QNum";

---

希望这能奏效

请将示例数据和预期结果添加到您的问题中。您的查询有语法错误。请参考官方文档，了解使用joinsWell的正确语法，语法错误是排序结果。-看见