我正在尝试构建一个发生多对多关系的SQL语句。基本上我想基于2个类别检索业务,一些业务包含在两个类别中并通过邮政编码查询。到目前为止,我得到了邮政编码部分,但它没有区分类别,我没有类别的表格,这也是最有效的方法吗?
到目前为止,这是SQL语句:
$query = "SELECT * FROM contacts WHERE zipcode in ( " . join(",", $zipcodes) . " ) ";
这是表格结构。非常简单。
`company_name` char(55) NOT NULL,
`phone` char(20) default NULL,
`email` char(40) default NULL,
`address` text,
`city` text,
`state` text,
`zipcode` varchar(5) default NULL,
`id` varchar(10) NOT NULL,
`geo_id` varchar(20) NOT NULL,
`website` varchar(40) NOT NULL,
`vendor_id` varchar(10) NOT NULL
`id` int(11) unsigned NOT NULL auto_increment,
`zip_code` varchar(5) character set utf8 collate utf8_bin NOT NULL,
`city` varchar(50) character set utf8 collate utf8_bin default NULL,
`county` varchar(50) character set utf8 collate utf8_bin default NULL,
`state_name` varchar(50) character set utf8 collate utf8_bin default NULL,
`state_prefix` varchar(2) character set utf8 collate utf8_bin default NULL,
`area_code` varchar(3) character set utf8 collate utf8_bin default NULL,
`time_zone` varchar(50) character set utf8 collate utf8_bin default NULL,
`lat` float NOT NULL,
`lon` float NOT NULL,
PRIMARY KEY (`id`),
KEY `zip_code` (`zip_code`)
我没有类别表。我将制作一个包含2个类别(零售和招待)的表格。问题是如何查询此表格以确定是否有联系人?
零售 待客 或两者......
答案 0 :(得分:0)
不太确定,因为细节水平相当低,但是:
$query = "SELECT * FROM contacts WHERE zipcode in ( " . join(",", $zipcodes) . " ) AND category1 = YOUR_DESIRED_VALUE AND category2 = YOUR_DESIRED_VALUE;";
或者只需要属于一个类别:
$query = "SELECT * FROM contacts WHERE zipcode in ( " . join(",", $zipcodes) . " ) AND (category1 = YOUR_DESIRED_VALUE OR category2 = YOUR_DESIRED_VALUE;");
答案 1 :(得分:0)
多对多关系通常需要一个表来存储关系。即,不是联系人表,不是类别表,而是单独的“contact_categories”表。
表格本身非常简单:
CREATE TABLE contact_categories (
contact_id VARCHAR(10) NOT NULL REFERENCES contact (id),
category_id INT NOT NULL
);
(使用此表,您甚至不需要单独的类别表,如果您记得第1类是零售,2则是招待,例如)
然后,如果联系人属于一个类别,则contact_categories表中有一行。如果它分为两类,则有两行,等等。
要获得类别1中的所有业务,那么,您的选择如下所示:
SELECT contacts.*
FROM contacts
JOIN contact_categories ON (contacts.id = contact_id);
如果您想通过邮政编码进行限制,只需添加WHERE子句:
SELECT contacts.*
FROM contacts
JOIN contact_categories ON (contacts.id = contact_id)
WHERE zipcode in ('12345','23456','90210');