MySQL查询需要更多时间执行?

本文介绍了MySQL查询需要更多时间执行?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 SELECT BB.NAME BranchName,VI.NAME Village,COUNT(BAC.CBSACCOUNTNUMBER) "No.Of Accounts", SUM(BAC.CURRENTBALANCE) SumOfAmount, SUM(CASE WHEN transactiontype = 'C' THEN amount ELSE 0 END) AS CreditTotal, SUM(CASE WHEN transactiontype = 'D' THEN amount ELSE 0 END) AS DebitTotal, SUM(CASE WHEN transactiontype = 'C' THEN amount WHEN transactiontype = 'D' THEN -1 * amount ELSE 0 END) AS CurrentBalance FROM CUSTOMER CU,APPLICANT AP,ADDRESS AD,VILLAGE VI,BANKBRANCH BB,BANKACCOUNT BAC LEFT OUTER JOIN accounttransaction ACT ON ACT.BANKACCOUNT_CBSACCOUNTNUMBER=BAC.CBSACCOUNTNUMBER AND DATE_FORMAT(ACT.TRANDATE,'%Y-%m-%d')<='2013-05-09' AND DATE_FORMAT(BAC.ACCOUNTOPENINGDATE,'%Y-%m-%d') <'2013-05-09' AND ACT.BANKACCOUNT_CBSACCOUNTNUMBER IS NOT NULL WHERE CU.CODE=AP.CUSTOMER_CODE AND BAC.ENTITY='CUSTOMER' AND BAC.ENTITYCODE=CU.CODE AND AD.ENTITY='APPLICANT' AND AD.ENTITYCODE=AP.CODE AND AD.VILLAGE_CODE=VI.CODE AND VI.STATE_CODE=AD.STATE_CODE AND VI.DISTRICT_CODE=AD.DISTRICT_CODE AND VI.BLOCK_CODE=AD.BLOCK_CODE AND VI.PANCHAYAT_CODE=AD.PANCHAYAT_CODE AND CU.BANKBRANCH_CODE=BB.CODE AND BAC.CBSACCOUNTNUMBER IS NOT NULL AND ACT.TRANSACTIONTYPE IS NOT NULL GROUP BY BB.NAME,VI.NAME LIMIT 10; and below is my explain plan id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE AD index ADDRESS_ENTITYCODE ADDRESS_ENTITYCODE 598 NULL 47234 Using where; Using index; Using temporary; Using filesort 1 SIMPLE VI ref PRIMARY PRIMARY 62 fiserveraupgb.AD.VILLAGE_CODE 1 Using where 1 SIMPLE AP eq_ref PRIMARY,AppCodeIndex PRIMARY 62 fiserveraupgb.AD.ENTITYCODE 1 1 SIMPLE BAC ref BANKACCOUNT_ENTITYCODE BANKACCOUNT_ENTITYCODE 63 fiserveraupgb.AP.CUSTOMER_CODE 1 Using where; Using index 1 SIMPLE CU eq_ref PRIMARY,CustCodeIndex PRIMARY 62 fiserveraupgb.AP.CUSTOMER_CODE 1 1 SIMPLE BB ref PRIMARY,Bankbranch_CodeName PRIMARY 62 fiserveraupgb.CU.BANKBRANCH_CODE 1 1 SIMPLE ACT index NULL accounttransaction_sysidindes 280 NULL 22981 Using where; Using index; Using join buffer

MySQL服务器版本5.5，我正在使用mysql工作台，下面是我的查询，它需要13分钟才能执行，请建议我为所涉及的所有列创建索引的最佳方法.

Mysql server version 5.5 and I am using mysql workbench below is my query it is taking 13 min to execute, please suggestion the best method I have created the indexes for all the columns which are involved.

推荐答案

您主要需要在联接和where子句中使用的列上建立索引.其他索引不会为您的select语句增加价值，也不会降低插入和更新的速度.

You mainly need indexes on columns that are used in joins and in your where clause. Other indexes don't add value for your select statements and slow down your inserts and updates.

在这种情况下，您将在函数中使用列值.因此，无法有效使用索引.

In this case, you're using the column values in functions. Due to this the indexes cannot be used efficiently.

这样的表达式效率很低:

An expression like this is very inefficient:

DATE_FORMAT(ACT.TRANDATE,'%Y-%m-%d')<='2013-05-09'

由于所有TRANDATES都转换为其值的字符串表示形式，因此会导致很多字符串转换.这些值需要临时存储并且不进行索引，因此除转换外，不再使用ACT.TRANDATE上的任何索引.这可能会导致在您的解释计划末尾相当昂贵的使用连接缓冲区".

It causes a lot of string conversions, because all TRANDATES are converted to a string representation of their value. These values need to be temporarily stored and are not indexed, so apart from the conversion, any index on ACT.TRANDATE is no longer used. That is probably causing the rather expensive 'Using join buffer' at the end of your explain plan.

而是将字符串"2013-05-09"转换为日期值，并将该值用作查询中的常量或参数.

Rather convert the string '2013-05-09' to a date value and use this value as a constant in or parameter for your query.

另一件事是，不是为单独的列创建单独的索引，而是为在where和/或联接中使用的一组列创建一个索引.例如这部分:

Another thing to do, is create not separate indexes for separate columns, but one index for a group of columns that is used in a where and/or join. For instance this part:

AD.ENTITY = 'APPLICANT' AND AD.ENTITYCODE = AP.CODE AND AD.VILLAGE_CODE = VI.CODE

在ENTITY，ENTITYCODE和VILLAGE_CODE列上同时具有一个索引要比为它们中的每一个都拥有单独的索引更有效.并且可能也包括其他列.

Having one index on the columns ENTITY, ENTITYCODE, and VILLAGE_CODE together would be more efficient than having a separate index for each of them. And it may help to include the other columns as well.

最后:如果保证一个列或多个列的组合是唯一的，请添加唯一索引.选择时速度稍快.

And last: If a column or combination of columns is guaranteed to be unique, ad a unique index. It is slightly faster in selects.

一般建议:不要将旧的联接语法与ansi联接混合使用.它使您的查询难以阅读.

A general advise: Don't mix old join syntax with ansi joins. It makes your query hard to read.

这些提示(除了最后一个提示)应该可以加快查询速度，但是它仍然很慢，具体取决于数据量，硬件和负载.

These hints (apart from the last one) should speed up your query, but it can still be slow, depending on the amount of data, the hardware and the load.