Question

请参阅下面的SQL查询，它似乎运行良好。它允许我通过邮政编码或城镇搜索记录。

用户在文本框中输入邮政编码或城镇。

uk_postcodes表中有一个邮政编码列表（BB1，BB2，BB3等）。

如果用户输入BB2或BB2 XXX，则会显示在BB2区域内发送的商店记录列表。（在进入SQL查询之前，我使用PHP获取邮政编码的第一部分）

如果用户输入Blackburn，则会显示具有默认投放区域的商店列表（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')";

这个SQL查询好吗？或者可以改进什么或使其变小？

Answer 1

你可以使用一个控制变量，一些是

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

$ myflagcontrol确定当前用户选择

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;
}

Answer 2

使用UNION ALL比使用UNION更快，因为不需要进行明确的检查。在这种情况下，除非有人住在一个也是邮政编码的城镇，否则你不需要这笔费用！

如何改进SQL查询

2 个答案: