SELECT m.* from message m
INNER JOIN `case` c on c.EbayAccountId=m.EbayAccountId
WHERE m.EbayAccountId is not NULL and m.id>0
GROUP BY m.EbayAccountId
LIMIT 10;
1 SIMPLE m index PRIMARY,IDX_Id_Created,IDX_EbayAccountId_Created IDX_EbayAccountId_Created 149 110 Using where
1 SIMPLE c ref IX_EbayAccountId_Created IX_EbayAccountId_Created 144 customerservicesystem.m.EbayAccountId 176 Using index
表結構：
CREATE TABLE `message` (
`Id` char(36) NOT NULL,
`EbayId` varchar(20) NOT NULL,
`ExternalId` varchar(100) DEFAULT NULL ,
`Subject` text NOT NULL ,
`Body` longtext ,
`CustomerAccount` varchar(100) NOT NULL ,
`EbayAccountId` char(36) NOT NULL ,
`MessageTime` datetime NOT NULL ,
`EbayItemId` varchar(20) DEFAULT NULL COMMENT 'ItemNo',
`ItemId` char(36) DEFAULT NULL COMMENT '產品Id',
`ItemCode` varchar(50) DEFAULT NULL COMMENT '產品名稱SKU/SPU',
`ItemType` int(11) DEFAULT NULL COMMENT '產品型別',
`EbayMessageType` varchar(50) NOT NULL,
`EbayQuestionType` varchar(50) NOT NULL,
`IsReceived` tinyint(4) NOT NULL COMMENT '區分訊息來源：true:表示買家發送過來接收的訊息，fase表示回復的訊息',
`HasReplied` tinyint(4) NOT NULL COMMENT '是否已回復',
`HasRead` tinyint(4) NOT NULL COMMENT '是否已讀',
`OwnerId` char(36) DEFAULT NULL COMMENT '處理客服ID',
`OwnerName` varchar(50) DEFAULT NULL COMMENT '處理客服名稱',
`Level` int(11) NOT NULL COMMENT '級別: Normal:標準,Urgent:緊急,NoNeedReply:不必回復',
`IsAfterSale` tinyint(4) NOT NULL COMMENT '是否售后',
`Created` datetime NOT NULL COMMENT '記錄生成日期',
`BodyGzip` longblob,
PRIMARY KEY (`Id`),
KEY `IDX_EBAYID` (`EbayId`),
KEY `IDX_OWNERID_ISRECEIVED` (`OwnerId`,`IsReceived`),
KEY `IX_CustomerAccount` (`CustomerAccount`),
KEY `IX_EbayItemId` (`EbayItemId`),
KEY `IDX_Id_Created` (`Id`,`Created`),
KEY `IX_ExternalId` (`ExternalId`),
KEY `IDX_Created` (`Created`),
KEY `IDX_EbayAccountId_Created` (`EbayAccountId`,`Created`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
uj5u.com熱心網友回復：
檢查一下滿足條件的資料量，group by 后的資料量和總資料量雖然有 limit 10，但這個作用于 group by 的結果，所以如果資料量非常大的話，肯定是要處理長時間的
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標籤：MySQL
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