如何編寫此MySQL查詢以獲取正確的信息？ （子查詢，多個子查詢）

Question

這裏是我的工作查詢：

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

我有麻煩搞清楚是怎麼寫的這個添加更多rentcondition限制器向下搜索結果進行過濾這個名單是什麼。

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

數據：

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

正如埃裏克·J表示爲註釋：

嘗試改變=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，也可以使用顯式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

爲什麼不：

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連接語法：

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