mysql - 在 MySQL 中为连接某个表创建索引

Question

我对 MySQL 数据库有如下 SQL 查询:

SELECT
    count(*) AS count,
    sum(total) AS total
FROM
    vtiger_salesorder
INNER JOIN vtiger_crmentity ON vtiger_crmentity.crmid = vtiger_salesorder.salesorderid
INNER JOIN vtiger_sobillads ON vtiger_salesorder.salesorderid = vtiger_sobillads.sobilladdressid
INNER JOIN vtiger_soshipads ON vtiger_salesorder.salesorderid = vtiger_soshipads.soshipaddressid
INNER JOIN vtiger_salesordercf ON vtiger_salesordercf.salesorderid = vtiger_salesorder.salesorderid
INNER JOIN vtiger_account ON vtiger_account.accountid = vtiger_salesorder.accountid
LEFT JOIN vtiger_users ON vtiger_users.id = vtiger_salesordercf.cf_456
LEFT JOIN vtiger_contactdetails ON vtiger_salesorder.contactid = vtiger_contactdetails.contactid
LEFT JOIN vtiger_soshop ON vtiger_soshop.salesorderid = vtiger_salesorder.salesorderid
WHERE
    vtiger_crmentity.deleted = 0
ORDER BY
    vtiger_crmentity.modifiedtime DESC;

Please click here to show Explain above SQL

您能帮我创建一些索引来提高此查询的性能吗？ 谢谢

Answer 1

您可以尝试以下三个复合索引是否有改善。

CREATE INDEX idxCrmidDeleted
             ON vtiger_crmentity
                (crmid,
                 deleted);

CREATE INDEX idxSalesorderidAccountidContactid
             ON vtiger_salesorder
                (salesorderid,
                 accountid,
                 contactid);

CREATE INDEX idxSalesorderidCf_456
             ON vtiger_salesordercf
                (salesorderid,
                 cf_456);

检查执行计划是否被执行。

total 列从何而来？如果它来自上面索引的任何表，也可以尝试像上面这样的索引，但另外将 total 作为最后一列。例如

CREATE INDEX idxSalesorderidAccountidContactid
             ON vtiger_salesorder
                (salesorderid,
                 accountid,
                 contactid,
                 total);

如果total位于vtiger_salesorder中。那么有可能只单独查询索引。