如何提高SQL查询速度

Question

我需要建议，如果这种调整是可能的。

表：

CREATE TABLE UTIL_DAY (
  CompID varchar(15) collate utf8_czech_ci NOT NULL,
  TestplanID int(10) unsigned NOT NULL default '0',
  FromDate datetime NOT NULL default '0000-00-00 00:00:00',
  ToDate datetime NOT NULL default '0000-00-00 00:00:00',
  Interval int(11) NOT NULL default '0',
  Variant varchar(25) collate utf8_czech_ci default NULL,
  WO_ID int(11) default NULL,
  SAPTime int(5) default NULL,
  UseTime int(5) NOT NULL,
  MeasureCount int(10) unsigned NOT NULL,
  KEY CompID (CompID),
  KEY TestplanID (TestplanID),
  KEY WO_ID (WO_ID),
  KEY FromDate (FromDate),
  KEY Variant (Variant)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_czech_ci;

当前查询：

UPDATE UTIL_DAY UDAY SET TestplanID = (SELECT TestplanID 
                                       FROM (SELECT UD_U.Variant,UD_U.WO_ID,VS.TestplanID 
                                             FROM (SELECT UD.Variant,UD.WO_ID 
                                                   FROM UTIL_DAY UD WHERE SUBSTR(CompID,1,3) <> 'AOI' 
                                                   GROUP BY UD.Variant,UD.WO_ID) UD_U 
                                             JOIN VARIANTS V ON UD_U.Variant = V.Variant 
                                             JOIN VARIANT_STATUS VS ON V.VariantID = VS.VariantID 
                                             JOIN TESTPLANS_WO_ID TW ON UD_U.WO_ID = TW.WO_ID 
                                             WHERE VS.TestplanID = TW.TestplanID 
                                             GROUP BY UD_U.Variant,UD_U.WO_ID ) TP 
                                       WHERE TP.Variant = UDAY.Variant AND TP.WO_ID = UDAY.WO_ID)

我的更新是临时表：

CREATE TEMPORARY TABLE UTIL_DAY_TEMP (
Variant varchar(25) COLLATE 'utf8_czech_ci' NOT NULL,
WO_ID int unsigned NOT NULL,
TestplanID int unsigned NOT NULL,
PRIMARY KEY Variant_WO_ID (Variant, WO_ID)) COMMENT='' ENGINE='InnoDB' COLLATE 'utf8_czech_ci';
INSERT IGNORE INTO UTIL_DAY_TMP (SELECT UD_U.Variant,UD_U.WO_ID,VS.TestplanID 
                FROM (SELECT UD.Variant,UD.WO_ID 
            FROM UTIL_DAY UD WHERE SUBSTR(CompID,1,3) <> 'AOI' 
            GROUP BY UD.Variant,UD.WO_ID) UD_U 
      JOIN VARIANTS V ON UD_U.Variant = V.Variant 
      JOIN VARIANT_STATUS VS ON V.VariantID = VS.VariantID 
      JOIN TESTPLANS_WO_ID TW ON UD_U.WO_ID = TW.WO_ID 
      WHERE VS.TestplanID = TW.TestplanID 
      GROUP BY UD_U.Variant,UD_U.WO_ID);
 UPDATE UTIL_DAY UDAY SET TestplanID = (SELECT TestplanID 
                                        FROM UTIL_DAY_TEMP TP 
                                         WHERE TP.Variant = UDAY.Variant AND TP.WO_ID = UDAY.WO_ID);

这一改进将查询速度提高了400%，超过两百万行。但是这种改进有同样的结果吗？感谢您的回答。

Answer 1

首先，使用

mysql中的EXPLAIN命令。

在此之后，确定是否有索引可以帮助您(警告:不要失控地创建索引)此外，还可以查看mysql上的复合索引文档