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我真的在为以下两个查询而苦苦挣扎。我有两张表都有超过一百万条记录。第一个查询运行 30 秒，第二个查询运行超过 7 分钟。

基本上我想根据 Lot 获得计数 class.id 和 scan_layers.id。最有效的方法是什么？

select count(class.id), count(scan_layers.id), Lot, Verified from class left join scan_layers on (class.ScanLayer = scan_layers.id) group by Lot;

select count(class.id), count(distinct scan_layers.id), Lot, Verified from class left join scan_layers on (class.ScanLayer = scan_layers.id) group by Lot;

当我解释它时，他们都给了我同样的解释。

+----+-------------+--------------------+--------+---------------+------------------------+---------+----------------------------------+---------+----------------------------------------------+
| id | select_type | table              | type   | possible_keys | key                    | key_len | ref                              | rows    | Extra                                        |
+----+-------------+--------------------+--------+---------------+------------------------+---------+----------------------------------+---------+----------------------------------------------+
|  1 | SIMPLE      | class | index  | NULL          | defects_scan_layers_fk | 4       | NULL                             | 4417159 | Using index; Using temporary; Using filesort |
|  1 | SIMPLE      | scan_layers        | eq_ref | PRIMARY       | PRIMARY                | 4       | cdb.class.ScanLayer |       1 |                                              |
+----+-------------+--------------------+--------+---------------+------------------------+---------+----------------------------------+---------+----------------------------------------------+

CREATE TABLE `class` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`ScanLayer` int(10) unsigned NOT NULL,
`Type` enum('Regular','Critical') NOT NULL DEFAULT 'Regular',
PRIMARY KEY (`id`),
UNIQUE KEY `Defect_UNIQUE` (`ScanLayer`),
KEY `class_scan_layers_fk` (`ScanLayer`),
CONSTRAINT `class_scan_layers_fk` FOREIGN KEY (`ScanLayer`) REFERENCES `scan_layers` (`id`) ON UPDATE CASCADE
) ENGINE=InnoDB


CREATE TABLE `scan_layers` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`LayerInfo` int(10) unsigned NOT NULL,
`Lot` varchar(45) NOT NULL DEFAULT 'DEFAULT',
`PhysicalID` int(10) unsigned NOT NULL,
`Scanned` datetime DEFAULT NULL,
`ScannedMachine` int(10) unsigned DEFAULT NULL,
`DefectsCount` int(10) unsigned NOT NULL DEFAULT '0',
`MovesCount` int(10) unsigned NOT NULL DEFAULT '0',
`Verified` datetime DEFAULT NULL,
`VerifiedMachine` int(10) unsigned DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `ScanLayer_UNIQUE` (`LayerInfo`,`Lot`,`PhysicalID`),
KEY `scan_layers_layer_infos_fk` (`LayerInfo`),
KEY `scan_layers_scanned_machines_fk` (`ScannedMachine`),
KEY `scan_layers_verified_machines_fk` (`VerifiedMachine`),
KEY `scan_layers_verified` (`Verified`),
KEY `scan_layers_lot` (`Lot`),
CONSTRAINT `scan_layers_layer_infos_fk` FOREIGN KEY (`LayerInfo`) REFERENCES `layer_infos` (`id`) ON UPDATE CASCADE,
CONSTRAINT `scan_layers_scanned_machines_fk` FOREIGN KEY (`ScannedMachine`) REFERENCES `machines` (`id`) ON UPDATE CASCADE,
CONSTRAINT `scan_layers_verified_machines_fk` FOREIGN KEY (`VerifiedMachine`) REFERENCES `machines` (`id`) ON UPDATE CASCADE,
) ENGINE=InnoDB

非常感谢！

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0 回答 0