[英]MYSQL - Select query with multiple OR conditions is Slow
我有一個超過200萬行的表,我需要在循環中快速對其進行選擇查詢。
SELECT ID,WebSite FROM `CompanyData` WHERE A1='data1' OR A2='data2' OR A3='data3'
這需要300毫秒。 我覺得不應該花那么多時間。 這是該查詢的解釋:
--------+---------------------------------------------------------------------------------------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------+-------+---------------+------+---------+------+---------+-------------------------------------------+
| 1 | SIMPLE | CompanyData | index | A1,A2,A3 | A1,A2,A3 | 153,153,153 | NULL | 3 | Using union(A1,A2,A3); Using where |
+----+-------------+----------+-------+---------------+------+---------+------+---------+-------------------------------------------+
這是表的結構:
CREATE TABLE `CompanyData` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`WebSite` varchar(150) DEFAULT NULL,
`CompanyName` varchar(200) DEFAULT NULL,
`A1` varchar(150) DEFAULT NULL,
`A2` varchar(150) DEFAULT NULL,
`A3` varchar(150) DEFAULT NULL,
PRIMARY KEY (`ID`),
UNIQUE KEY `WebSite` (`WebSite`,`CompanyName`),
KEY `CompanyName` (`CompanyName`),
KEY `A1` (`A1`),
KEY `A2` (`A2`),
KEY `A3` (`A3`)
) ENGINE=InnoDB AUTO_INCREMENT=3931223 DEFAULT CHARSET=latin1
最近,我在表中又插入了1000萬條記錄。 然后,相同的查詢大約需要3秒。
請提出一種改進選擇查詢查找的方法。 甚至我也准備重組表。
謝謝
MySQL很難使用OR
來優化條件。 您最好嘗試:
SELECT ID, WebSite
FROM `CompanyData`
WHERE A1 = 'data1'
UNION
SELECT ID, WebSite
FROM `CompanyData`
WHERE A2 = 'data2'
UNION
SELECT ID, WebSite
FROM `CompanyData`
WHERE A3 = 'data3';
請注意,這使用UNION
代替UNION ALL
。 帶有UNION ALL
的替代版本如下所示(假定值從不NULL
):
SELECT ID, WebSite
FROM `CompanyData`
WHERE A1 = 'data1'
UNION ALL
SELECT ID, WebSite
FROM `CompanyData`
WHERE A2 = 'data2' AND A1 <> 'data1'
UNION ALL
SELECT ID, WebSite
FROM `CompanyData`
WHERE A3 = 'data3' AND A1 <> 'data1' AND A2 <> 'data2';
對於此查詢,最佳索引是復合索引: (A1, ID, WebSite)
, (A2, A1, ID, Website)
和(A3, A1, A2, ID, WebSite)
。
跨列展開的數組是有問題的。
試試這個...
CREATE TABLE `CompanyData` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`WebSite` varchar(150) DEFAULT NULL,
`CompanyName` varchar(200) DEFAULT NULL,
PRIMARY KEY (`ID`),
UNIQUE KEY `WebSite` (`WebSite`,`CompanyName`),
KEY `CompanyName` (`CompanyName`),
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
CREATE TABLE `Stuff` (
`CompanyID` int(11) NOT NULL
`A` varchar(150) NOT NULL,
PRIMARY KEY (A, CompanyID)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
SELECT c.ID, c.WebSite
FROM CompanyData AS c
JOIN Stuff AS s ON c.ID = s.CompanyID
WHERE s.A IN ('data1', 'data2', 'data3');
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