MYSQL 删除表本身的 NOT IN 子查询

Question

我有以下查询，显示具有特定 margin 水平的账户列表:

SELECT
    crm_margincall.id,
    crm_margincall.CreationTime,
    ba.name AS crm_bankaccount_id,
    crm_margincall.name,
    crm_margincall.MarginCallLevel,
    crm_margincall.UseOfEquityForMargin,
    crm_margincall.MarginRequired,
    crm_margincall.NetEquityForMargin,
    crm_margincall.MarginDeficit,
    crm_margincall.balance,
    crm_margincall.deposited,
    crm_margincall.prefunded,
    crm_margincall.required
FROM 
    crm_margincall
LEFT JOIN
    crm_bankaccount ba ON crm_margincall.crm_bankaccount_id = ba.id
WHERE 
    crm_margincall.name = 'MarginCall' 
AND 
    crm_margincall.MarginCallLevel >= 100
AND 
    crm_margincall.crm_account_id NOT IN 
    (
    SELECT 
        x.crm_account_id 
    FROM 
        crm_margincall x 
    WHERE 
        x.crm_account_id = crm_margincall.crm_account_id 
    AND 
        x.name = 'LevelDrop' 
    AND 
        x.MarginCallLevel < 100 
    AND 
        x.id > crm_margincall.id
    )
ORDER BY 
    id
DESC

此查询在约 22.500 条记录的表上运行需要 >10 秒，这是由定义 NOT IN 部分的子查询引起的(尝试过 NOT EXISTS，速度并不快)。我怎样才能加入这个表本身来达到同样的效果？

Answer 1

This query, on a table of ~22.500 records takes >10 seconds to run, this is caused by the subquery defining the NOT IN section (tried NOT EXISTS, isnt much faster). How can I join this table on itself to achieve the same effect?

这可以通过多种方式完成，但扫描 22500 条记录需要 10"意味着硬件问题或非常低效的 JOIN。

后者最可能的原因是索引缺失或索引配置错误，要对此进行调查，您需要发出 EXPLAIN:

EXPLAIN SELECT ...

完全在黑暗中拍摄，从所使用的选定列来看，我会尝试

 CREATE INDEX test_index ON crm_margincall(name, crm_account_id, MarginCallLevel, id)

其他改进可能是可能的，但您需要在 SQLfiddle 中准备一个包含一些假数据的示例结构，以真正允许调试。