php正则表达式去掉sql里面的order by

在sqlserver里面，例如这样的语句会报错： 

select count(1) from ( select * from aaa order by productid ) 

除非另外还指定了 TOP、OFFSET 或 FOR XML，否则，ORDER BY 子句在视图、内联函数、派生表、子查询和公用表表达式中无效。

正则表达式去掉sql里面的order by

$sql = "select * from (select * from  t_x Order      by ( id) Asc , xh desc    
    union all 
     select * from t_y order by xsdfx desc) sss order       by (SDf) group by ddk 
     UNION  all select * from xx where xid>100 ) as t";
echo '$sql='.$sql.'<br/><br/> ';

$regex = '/(order\s*by\s*.*desc)|(order\s*by\s*.*asc)|(order\s*by\s*\S+)/i';

preg_match_all($regex, $sql . " ", $matches);
//print_r($matches); echo '<br/>';

$sql = str_ireplace($matches[0], ' ', $sql);

echo '去掉order by后：'.$sql;

但是，如果 order by 后面还有 case when 之类的复杂语句的话就难处理了。

 

另一种方法是 在 select 后 加上 top 100 percent 

select count(1) from ( select top 100 percent * from aaa order by productid )