我有两张table：表1：

CREATE TABLE `lk_transaction_types` (
  `transactionTypeID` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `isActive` tinyint(2) unsigned NOT NULL,
  `code` varchar(8) NOT NULL,
  `description` varchar(150) NOT NULL,
  `isInbound` tinyint(2) unsigned NOT NULL DEFAULT '1',
  `isOutbound` tinyint(2) unsigned NOT NULL DEFAULT '1',
  PRIMARY KEY (`transactionTypeID`)
) ENGINE=InnoDB AUTO_INCREMENT=32 DEFAULT CHARSET=utf8;

表2：

CREATE TABLE `ediLoad` (
  `loadID` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `processID` int(10) unsigned NOT NULL,
  `success` tinyint(2) unsigned NOT NULL DEFAULT '0',
  `transactionTypeID` tinyint(2) unsigned DEFAULT NULL,
  `escoID` int(10) unsigned DEFAULT NULL,
  `ldcID` int(10) unsigned DEFAULT NULL,
  `commodityType` tinyint(3) unsigned NOT NULL DEFAULT '0',
  `filename` varchar(150) NOT NULL,
  `loadDate` datetime NOT NULL,
  `processed` tinyint(2) unsigned NOT NULL DEFAULT '0',
  `processedDate` datetime DEFAULT NULL,
  `dataApplied` tinyint(2) unsigned NOT NULL DEFAULT '0',
  `dataAppliedDate` datetime DEFAULT NULL,
  `errorID` tinyint(3) unsigned DEFAULT NULL,
  `error` tinyint(2) unsigned DEFAULT '0',
  `warning` tinyint(2) unsigned DEFAULT '0',
  PRIMARY KEY (`loadID`),
  KEY `idx_processID` (`processID`,`transactionTypeID`,`escoID`),
  KEY `idx_escoID` (`escoID`),
  KEY `idx_filename` (`success`,`filename`),
  KEY `idx_bulk` (`processed`,`loadDate`),
  KEY `idx_loadDate` (`loadDate`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=35086005 DEFAULT CHARSET=utf8;

尝试运行简单查询时，它没有使用lk\ U transaction\ U types表上的主键：

SELECT COUNT(0)
FROM edi.ediLoad l
INNER JOIN edi.lk_transaction_types lk 
  ON  lk.transactionTypeID = l.transactionTypeID
WHERE l.escoID = 2
AND lk.isActive = 1
AND lk.isInbound = 1;

查询速度很慢。所以我跑去解释

EXPLAIN SELECT COUNT(0)
FROM edi.ediLoad l
INNER JOIN edi.lk_transaction_types lk 
  ON  lk.transactionTypeID = l.transactionTypeID
WHERE l.escoID = 2
AND lk.isActive = 1
AND lk.isInbound = 1;

这是回报

id  select_type table   partitions  type    possible_keys   key key_len ref rows    filtered    Extra
1   SIMPLE  lk  NULL    ALL PRIMARY NULL    NULL    NULL    31  3.23    Using where
1   SIMPLE  l   NULL    ref idx_escoID  idx_escoID  5   const   71580   10.00   Using where

这看起来像是一个简单的查询，主键上只有一个连接。为什么不使用主键？我甚至尝试将“force index for join（primary）”添加到连接中，但它仍然不使用主键。任何帮助都会很好。谢谢！