如何编写此MySQL查询以获取正确的信息？ （子查询，多个子查询）

Question

以下是我正在处理的查询：

SELECT `unitid`, `name` FROM apartmentunits
WHERE aptid = (
    SELECT `aptid` FROM rentconditionsmap WHERE rentcondid = 1 AND condnum = 1
)

我无法搞清楚如何编写这个以添加更多租金条件限制器以更多地过滤此列表。

SELECT `aptid` FROM rentconditionsmap WHERE rentcondid = 1 AND condnum = 1

数据：

CREATE TABLE IF NOT EXISTS `rentconditionsmap` (
   `rcid` bigint(10) unsigned NOT NULL AUTO_INCREMENT, 
   `rentcondid` int(3) unsigned NOT NULL, 
   `condnum` tinyint(3) unsigned NOT NULL, 
   `aptid` bigint(10) unsigned DEFAULT NULL, 
   PRIMARY KEY (`rcid`), KEY `aptid` (`aptid`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=18 ;

INSERT INTO `rentconditionsmap` 
  (`rcid`, `rentcondid`, `condnum`, `aptid`) 
VALUES 
  (1, 1, 1, 1), 
  (2, 2, 1, 1), 
  (3, 3, 0, 1), 
  (4, 4, 1, 1), 
  (5, 8, 0, 1);

CREATE TABLE IF NOT EXISTS `apartmentunits` (
  `unitid` bigint(10) NOT NULL AUTO_INCREMENT, 
  `aptid` bigint(10) NOT NULL, 
  `name` varchar(6) NOT NULL, 
  `verified` tinyint(1) NOT NULL DEFAULT '0', 
  `rentcost` int(4) unsigned DEFAULT NULL, 
  `forrent` tinyint(1) NOT NULL DEFAULT '0', 
  `unittypekey` varchar(2) DEFAULT NULL, 
  `sqft` smallint(6) DEFAULT NULL, 
  PRIMARY KEY (`unitid`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=121 ;

INSERT INTO `apartmentunits` 
  (`unitid`, `aptid`, `name`, `verified`, `rentcost`, `forrent`, `unittypekey`, `sqft`) 
VALUES 
  (1, 1, '3', 1, 540, 0, '2B', NULL), 
  (2, 1, '5', 1, NULL, 0, '2B', NULL), 
  (3, 1, '7', 1, NULL, 0, '2B', NULL), 
  (53, 1, '1', 1, NULL, 0, '2B', NULL), 
  (54, 1, '2', 1, NULL, 0, '2B', NULL), 
  (55, 1, '4', 1, 570, 0, '2B', NULL), 
  (56, 1, '6', 1, NULL, 0, '2B', NULL), 
  (57, 1, '8', 1, NULL, 0, '2B', NULL), 
  (58, 1, '9', 1, NULL, 0, '2B', NULL), 
  (59, 1, '10', 1, NULL, 0, '2B', NULL), 
  (60, 1, '11', 1, NULL, 0, '2B', NULL);

Answer 1

为什么不：

SELECT unitid, name
FROM apartmentunits a INNER JOIN rentconditionsmap r on a.aptid = r.aptid
WHERE (rentcondid = 1 and condnum = 1) OR (rentcondid = 2 and condnum = 2)

Answer 2

使用ANSI-92连接语法：

SELECT au.unitid, 
       au.name 
  FROM APARTMENTUNITS au
  JOIN RENTCONDITIONSMAP rcm ON rcm.aptid = au.aptid
                            AND rcm.rentcondid = 1
                            AND rcm.condnum = 1

Answer 3

正如Eric J所说：

  

尝试将=更改为IN

SELECT `unitid`, `name` FROM apartmentunits
WHERE `aptid` IN (
    SELECT `aptid` FROM rentconditionsmap WHERE rentcondid = 1 AND condnum = 1
)

Answer 4

使用JOIN（以下是连接的SQL语法，或者您可以使用显式的INNER JOIN）。

SELECT apartmentunits.unitid, apartmentunits.name 
FROM apartmentunits, rentconditionsmap
WHERE apartmentunits.aptid = rentconditionsmap.aptid
AND rentconditionsmap.rentcondid = 1
AND rentconditionsmap.condnum = 1
-- AND whatever else...