Question

例如：这是3个场地。 A，B，C 用户可以将学生分配到这个3.并且一旦分配，它将从下拉列表中删除，因此用户不能再添加它们，之后留下'B'和'C'可用。我如何使用查询语句？

Answer 1

SELECT *
FROM venues
WHERE venues.id NOT IN (
  SELECT venue_id
  FROM students
  WHERE id=:studentid
)

Answer 2

表单提交上的

PHP

//Store all possible options
$opts = array("a","b","c");

//Create array from selected option
$selected = array($_POST['selectMenu']);

//Use array_diff to remove selected from options array
$revisedOpts = array_diff($opts,$selected);

//At this point, you can use $revisedOpts to make an SQL query
....

HTML / PHP的

<select name='selectMenu'><?php
//Echo out remaining options
foreach($revisedOpts as $v) {
  echo "<option>".$v."</option>";
}
?></select>

分配和删除关闭下拉列表

2 个答案: