### update
修改表数据
update($table, $data, $where)
* ##### table [string]
表名.
* ##### data [array]
修改的数据.
* ##### where (optional) [array]
WHERE 条件.[可选]
Return: [number] 受影响的行数.
你可以修改没有序列化的数组, 并且能使用 [+], [-], [*], [/] 来做运算
~~~
$database->update("account", [
"type" => "user",
// All age plus one
"age[+]" => 1,
// All level subtract 5
"level[-]" => 5,
// All score multiplied by 2
"score[*]" => 2,
// Like insert, you can assign the serialization
"lang" => ["en", "fr", "jp", "cn", "de"],
"(JSON) fav_lang" => ["en", "fr", "jp", "cn", "de"],
// You can also assign # for using SQL functions
"#uid" => "UUID()"
], [
"user_id[<]" => 1000
]);
~~~
