的preg_match提取标识符和别名

Question

我试图从mysql命令标识符和别名BY和最亲密的问题，它可以帮助我是Removing aliases from a SQL select statement, using C# and regular expressions

function test($orderby) 
{ 
    if(preg_match('/(?<field>.*)(?:\s*|\s+AS\s+)?(?<alias>\w*)?/i', $orderby, $matches)){ 
     unset($matches[1]); 
     unset($matches[2]); 
     echo '<pre>'.htmlspecialchars(print_r($matches,true)).'</pre>'; 
    }else{ 
     echo '$orderby doest not matches'; 
    } 
} 

test("field");工作

Array 
(
    [0] => field 
    [field] => field 
    [alias] => 
) 

test("table.field");工作

Array 
(
    [0] => table.field 
    [field] => table.field 
    [alias] => 
) 

test("CONCAT(table.field1, ' ', table.field2) AS alias");不工作

Array 
(
    [0] => CONCAT(table.field1, ' ', table.field2) AS alias 
    [field] => CONCAT(table.field1, ' ', table.field2) AS alias 
    [alias] => 
) 

test("table.field alias");打印

Array 
(
    [0] => table.field alias 
    [field] => table.field alias 
    [alias] => 
) 

我需要例如3 [field] => CONCAT(table.field1, ' ', table.field2)和[alias] => alias在和实例4 [field] => table.field和[alias] => alias

我想要做的是

/ 
(?<field>.*)    #identifier 
(?:\s*|\s+AS\s+)?  # without spaces (examples 1 and 2), spaces (example 4) OR 'AS' (example 3) 
(?<alias>\w*)?   #alias 
/i 

我做错了什么？ 在此先感谢。

Answer 1

这种模式能适用于所有的示例工作：

/(?<field>.*?)((?:\s+|\s+AS\s+)(?<alias>\w+))?$/i 
      │ │  │   ┊   │ │┊│ 
      1 2  3   4   5 267 

1) Added not-greedy operator; 
2) Added capturing group for sub-groups AS/alias; 
3) Changed zero-or-more to one-or-more (at least one space is needed); 
4) Removed zero-or-one for subgroup AS (at least one space is needed); 
5) Changed zero-or-more to one-or-more (at least one char is needed); 
6) Moved zero-or-more from sub-group alias to group 2); 
7) Added end-of-line anchor. 

eval.in demo

新捕获组创建，所以你也$matches[3]取消设置：

unset($matches[1], $matches[2], $matches[3]); 

因为我们添加了endline anchor，所以我su提示你在函数的开头添加这一行：

$orderby = trim($orderby);