Question

$logged = $_SESSION['logged']; 

    $construct = "SELECT child.* 
       FROM products child 
       LEFT JOIN products parent on parent.sid=child.sid 
       WHERE parent.id = 
        '(SELECT productid 
        FROM subscribed 
        WHERE username=\"$logged\")' 
       AND parent.keyword != child.name 
       ORDER BY child.id DESC"; 

我無法使子查詢工作我得到錯誤的結果。父查詢很好，因爲我之前使用過它。這是我第一次使用一個對我來說很裸露的子查詢。

我想讓子查詢從'訂閱'表中獲取所有產品，其中username = $ logs。

這是我想要的，但在一個查詢中，檢查WHERE子句的差異。

$construct = "SELECT child.* 
       FROM products child 
       LEFT JOIN products parent on parent.sid=child.sid 
       WHERE parent.id= 
       'SUB QUERY RESULT 1' 
       AND parent.keyword != child.name 
       ORDER BY child.id DESC"; 

$construct = "SELECT child.* 
       FROM products child 
       LEFT JOIN products parent on parent.sid=child.sid 
       WHERE parent.id= 
       'SUB QUERY RESULT 2' 
       AND parent.keyword != child.name 
       ORDER BY child.id DESC"; 

$construct = "SELECT child.* 
       FROM products child 
       LEFT JOIN products parent on parent.sid=child.sid 
       WHERE parent.id= 
       'SUB QUERY RESULT 3' 
       AND parent.keyword != child.name 
       ORDER BY child.id DESC"; 

如何在不循環查詢的情況下在一個查詢中執行此操作。我甚至需要一個子查詢？

Answer 1

您可以使用一個內連接到你想要的東西：

$construct = "SELECT child.*   
    FROM products child   
    LEFT JOIN products parent on parent.sid=child.sid   
    INNER JOIN subscibed s ON (s.productid = parent.id) 
    WHERE s.username = '$logged' 
    AND parent.keyword != child.name   
    ORDER BY child.id DESC"; 

如果你想在三個查詢在一個連接做：

$construct = "SELECT child.*    
      FROM products child    
       LEFT JOIN products parent on (parent.sid = child.sid)    
      WHERE parent.id IN    
       (SELECT productid FROM table1 WHERE username= '$logged' 
       UNION 
        SELECT productid FROM table2 WHERE something = '$somethingelse' 
       UNION 
        SELECT productid FROM table3 WHERE otherthing = '$otherstuff' 
       )    
      AND parent.keyword != child.name    
      ORDER BY child.id DESC";