当mysql WHERE子句为空时,返回所有行

Question

$randomvariable=$_GET['randomvariable'];
$search="SELECT * from objects
          WHERE transactiontype='$randomvariable'
          order by id DESC";

现在如果$randomvariable是空的(没有),我希望它返回所有行.目前,如果它是空的,则不返回任何内容,因为它基本上不会从所有行中搜索任何内容.

Answer 1

$randomvariable = ESACPE_MYSQL_STRING($_GET['randomvariable']);
$search =
    "SELECT * FROM objects " .
    (empty($randomvariable) ? "" : "WHERE transactiontype='$randomvariable' ") .
    "ORDER BY id DESC";

对于ESCAPE_MYSQL_STRING您正在使用的任何MySQL驱动程序,转义字符串的相关函数在哪里.

另一种更模块化的方式:

$search = array(
    "select" => "SELECT * FROM objects",
    "where" => "WHERE transactiontype='$randomvariable'",
    "order" => "ORDER BY id DESC"
);

if (empty($randomvariable)) {
    unset($search["where"]);
}

$search = implode(' ', $search);

关于这一点的好处是,您可以轻松地添加,删除或更改任何情况的查询,轻松访问查询的任何部分.

您也可以CASE()在SQL中执行此操作,但它有点麻烦,您不应该期望良好的性能:

SELECT * FROM objects
WHERE transactiontype LIKE
    CASE WHEN '$randomvariable' = '' THEN
        '%'
    ELSE
        '$randomvariable'
    END CASE
ORDER BY id DESC

Answer 2

另一种方法：

if ($_GET['randomvariable'] != "") {
   $where = "transactiontype = " . $randomvariable;
} else {
   $where = "1";
}

$search = "SELECT * from objects WHERE " . $where . " ORDER BY id DESC";