Question

我正在使用某人的PHP脚本进行多次下拉，我在这方面遇到了麻烦。我想放ORDER BY，但我不知道放在哪里：

// define a string with the WHERE condition, and then the SELECT query
$where = isset($ar_where) ? ' WHERE '. implode($ar_where, ' AND') : '';
$sql = "SELECT DISTINCT `$col` FROM `$table`".$where;

这是代码。我试着这样做

$sql = "SELECT DISTINCT $col FROM $table".$where." ORDER BY 'make' DESC";

但是没有任何事情我试图让汽车按字母顺序排列

    // Here add the name of the table and columns that will be used for select lists, in their order
// Add null for 'links' if you don`t want to display their data too
$table = 'cars';
$ar_cols = array('year', 'make', 'model', 'null');

$preid = 'slo_';        // a prefix used for element's ID, in which Ajax will add <select>
$col = $ar_cols[0];     // the variable used for the column that wil be selected
$mine = $ar_cols[1];
$re_html = '';          // will store the returned html code

// if there is data sent via POST, with index 'col' and 'wval'
if(isset($_POST['col']) && isset($_POST['wval'])) {
  // set the $col that will be selected and the value for WHERE (delete tags and external spaces in $_POST)
  $col = trim(strip_tags($_POST['col']));
  $wval = "'".trim(strip_tags($_POST['wval']))."'";
}

$key = array_search($col, $ar_cols);            // get the key associated with the value of $col in $ar_cols
$wcol = $key===0 ? $col : $ar_cols[$key-1];     // gets the column for the WHERE clause
$_SESSION['ar_cols'][$wcol] = isset($wval) ? $wval : $wcol;    // store in SESSION the column and its value for WHERE

// gets the next element in $ar_cols (needed in the onchange() function in <select> tag)
$last_key = count($ar_cols)-1;
$next_col = $key<$last_key ? $ar_cols[$key+1] : '';

$conn = new mysqli($server, $user, $pass, $dbase);     // connect to the MySQL database

if (mysqli_connect_errno()) { exit('Connect failed: '. mysqli_connect_error()); }     // check connection

// sets an array with data of the WHERE condition (column=value) for SELECT query
for($i=1; $i<=$key; $i++) {
  $ar_where[] = '`'.$ar_cols[$i-1].'`='.$_SESSION['ar_cols'][$ar_cols[$i-1]];
}

// define a string with the WHERE condition, and then the SELECT query
$where = isset($ar_where) ? ' WHERE '. implode($ar_where, ' AND') : '';
//$sql = "SELECT DISTINCT `$col` FROM `$table`".$where; 
$sql = "SELECT DISTINCT $col FROM $table".$where." ORDER BY 'make' DESC";

$result = $conn->query($sql);       // perform the query and store the result

// if the $result contains at least one row
if ($result->num_rows > 0) {
  // sets the "onchange" event, which is added in <select> tag
  $onchg = $next_col!==null ? " onchange=\"ajaxReq('$next_col', this.value);\"" : '';

  // sets the select tag list (and the first <option>), if it's not the last column
  if($col!=$ar_cols[$last_key]) $re_html = ucfirst($col). ': <select name="'. $col. '"'. $onchg. '><option>- - -</option>';

  while($row = $result->fetch_assoc()) {
    // if its the last column, reurns its data, else, adds data in OPTION tags
    if($col==$ar_cols[$last_key]) $re_html .= '<br/>'. $row[$col];
    else $re_html .= '<option value="'. $row[$col]. '">'. $row[$col]. '</option>';
  }

  if($col!=$ar_cols[$last_key]) $re_html .= '</select> ';        // ends the Select list
}
else { $re_html = ''; }

$conn->close();

// if the selected column, $col, is the first column in $ar_cols
if($col==$ar_cols[0]) {
  // adds html code with SPAN (or DIV for last item) where Ajax will add the select dropdown lists
  // with ID in each SPAN, according to the columns added in $ar_cols
  for($i=1; $i<count($ar_cols); $i++) {
    if($ar_cols[$i]===null) continue;
    if($i==$last_key) $re_html .= '<div id="'. $preid.$ar_cols[$i]. '"> </div>';
    else $re_html .= '<br><span id="'. $preid.$ar_cols[$i]. '"> </span>';
  }

  // adds the columns in JS (used in removeLists() to remove the next displayed lists when makes other selects)
  $re_html .= '<script type="text/javascript">var ar_cols = '.json_encode($ar_cols).'; var preid = "'. $preid. '";</script>';
}
else echo $re_html;

Answer 1

ORDER BY位于WHERE子句之后，因此您的代码将是：

// define a string with the WHERE condition, and then the SELECT query
$where = isset($ar_where) ? ' WHERE '. implode($ar_where, ' AND') : '';
$sql = "SELECT DISTINCT `$col` FROM `$table`".$where." ORDER BY YOUR_COL_HERE ASC";

您可以使用ASC或DESC，具体取决于您是想要升序还是降序。

Answer 2

SQL关键字ORDER BY必须在查询结束时。

Answer 3

ORDER BY始终是最后一个SQL选项。有时您会在某些SQL查询中注意到ORDER BY ORDER是ASC DESC（升序或降序）;如果你想添加，你可以。例如，

 WHERE UserID = 1 AND ORDER BY FirstName DESC

我会将您的代码更改为：

// define a string with the WHERE condition, and then the SELECT query
$where = isset($ar_where) ? ' WHERE '. implode($ar_where, ' AND') : '';
// replace SoftField1 with the field you want to sort it by, 
// you may want to add ASC or DESC after the SortField1/2 if you 
// want a certain order
$order_by = ' ORDER BY `SortField1`, `SortField2`';
$sql = "SELECT DISTINCT `$col` FROM `$table`".$where.$order_by;

在下拉脚本中通过php提前订购

3 个答案: