如何改进SQL查询

查看下面的SQL查询，它似乎运行良好。它允许我通过邮编或城镇搜索记录。如何改进SQL查询

用户输入邮编或城市从文本框中。

从uk_postcodes表中有邮编列表（BB1，BB2，BB3等）。

如果用户输入BB2或BB2 XXX，它将显示一个在BB2区域发货的店铺记录列表。（我用PHP来获得邮政编码的第一部分，它进入SQL查询之前）

如果Blackburn用户类型，那么它会显示与默认送达地区的商店名单（D.shop_id = S.shop_id AND D.postcode_id = S.postcode_id）

$SQL = "(SELECT DISTINCT S.*, D.delivery_cost, D.postcode AS DeliveryAreaPostcode FROM shops AS S 
       JOIN shop_delivery_area AS D ON D.shop_id = S.shop_id 
       JOIN uk_postcodes AS P ON P.postcode_id = D.postcode_id 
        WHERE P.postcode = '$search' ORDER BY D.postcode) 
       UNION 
    (SELECT DISTINCT S.* , D.delivery_cost, D.postcode AS DeliveryAreaPostcode FROM shops AS S 
       JOIN shop_delivery_area AS D ON D.shop_id = S.shop_id AND D.postcode_id = S.postcode_id 
       JOIN uk_postcodes AS P ON P.postcode_id = D.postcode_id 
        WHERE S.town = '$search')";

是这个SQL查询很好？或者什么可以改进或使其变小？

来源

2011-11-16 I' ll-Be-Back

使用UNION ALL是因为不需要完成独特的检查，所以比使用UNION更快。在这种情况下，除非有人住在同样也是邮编的小镇，否则你不需要那些开销！

来源

2011-11-16 16:12:42

您可以使用一个控制变量，一些

$SQL = "SELECT DISTINCT S.*, D.delivery_cost, D.postcode AS DeliveryAreaPostcode 
     FROM shops AS S 
      JOIN shop_delivery_area AS D ON D.shop_id = S.shop_id 
      JOIN uk_postcodes AS P ON P.postcode_id = D.postcode_id 
     WHERE (P.postcode = '{0}' and '{1}' = 'postcode') 
     or (S.town = '{0}' and D.postcode_id = S.postcode_id and '{1}' = 'town') 
      ORDER BY D.postcode".format($search, $myflagcontrol);

$ myflagcontrol是如何确定的当前用户选择

格式是这里的虚拟函数代码

// Add format extension to string class 
String.prototype.format= function(){  
var str = this; 
for (var i = 0, l = arguments.length; i < l; i++) 
    str = str.replace("{" + i + "}", arguments[i]); 
return str; 
}

来源

2011-11-16 16:07:28

如何改进SQL查询

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