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

这里是我的工作查询：

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

我有麻烦搞清楚是怎么写的这个添加更多rentcondition限制器向下搜索结果进行过滤这个名单是什么。

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

正如埃里克·J表示为注释：

尝试改变=到IN

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

Answer 2

使用JOIN（下面是TSQL sintax的加入，也可以使用显式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... 

Answer 3

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 4

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