目前使用很笨的方法查詢出結果，想要把程式碼寫得更有彈性。現在想法是如何讓WHERE後的欄位名稱是可變動的變數，希望幫有解答

<?php
    if(isset($_GET['inquire']) && $_GET['inquire'] == 'inquire' ){
        if($_GET['classID'] != '*' && $_GET['publish'] != '*' ){
            $inpqire_sql = "SELECT `article`.`classID`,`article`.`title`,`article`.`publish`,`article`.`create_time`,`classify`.`classID`,
            `classify`.`className` FROM `article` LEFT JOIN `classify` on `article`.`classID` = `classify`.`classID`
            WHERE  `article`.`classID` = '{$_GET['classID']}' AND `article`.`publish` = '{$_GET['publish']}'
            ORDER BY `article`.`create_time` DESC  ";
        }elseif($_GET['classID'] != '*' && $_GET['publish'] = '*' ){
            $inpqire_sql = "SELECT `article`.`classID`,`article`.`title`,`article`.`publish`,`article`.`create_time`,`classify`.`classID`,
            `classify`.`className` FROM `article` LEFT JOIN `classify` on `article`.`classID` = `classify`.`classID`
            WHERE `article`.`classID` = '{$_GET['classID']}'
            ORDER BY `article`.`create_time` DESC  ";
        }elseif($_GET['classID'] = '*' && $_GET['publish'] != '*' ){
            $inpqire_sql = "SELECT `article`.`classID`,`article`.`title`,`article`.`publish`,`article`.`create_time`,`classify`.`classID`,
            `classify`.`className` FROM `article` LEFT JOIN `classify` on `article`.`classID` = `classify`.`classID`
            WHERE `article`.`publish` = '{$_GET['publish']}'
            ORDER BY `article`.`create_time` DESC  "; 
        }elseif($_GET['classID'] = '*' && $_GET['publish'] = '*' ){
            $inpqire_sql = "SELECT `article`.`classID`,`article`.`title`,`article`.`publish`,`article`.`create_time`,`classify`.`classID`,
            `classify`.`className` FROM `article` LEFT JOIN `classify` on `article`.`classID` = `classify`.`classID`
            ORDER BY `article`.`create_time` DESC  "; 
        };   

        $inquire_result = mysqli_query($link,$inpqire_sql);
        $inquire_row = mysqli_fetch_assoc($inquire_result);    
        }; 
?>

查詢語法

<div id="controller">
                <a href="article_Add.php">新增文章</a>
                    <form action="<?php $_SERVER['PHP_SELF']?>" method="get">
                        <span>類別:</span>
                            <select name="classID" id="classID">
                            <option value="*">All</option>
                            <?php do{ ?>
                                <option <? if($row_className['classID'] == $_GET['classID']){ echo "selected=true";  }; ?> value="<?php echo $row_className['classID'] ?>"><?php echo $row_className['className'] ?></option>
                            <?php }while($row_className = mysqli_fetch_assoc($result_className)) ?>
                            </select> 
                        <span>發布/不發布</span>
                        <select name="publish" id="publish">
                            <option value="*" <? if($_GET['publish'] == "*"){ echo "selected=true";  }; ?> >All</option>
                            <option value="1" <? if($_GET['publish'] == "1"){ echo "selected=true";  }; ?>>發布</option>
                            <option value="0" <? if($_GET['publish'] == "0"){ echo "selected=true";  }; ?>>不發布</option>
                        </select> 
                        <input type="hidden" name="inquire" value="inquire" >
                        <input type="submit" value="查詢" >
                    </form>
            </div>

下拉是選單