MYSQL remove NOT IN subquery on table itself - mysql

Question

I have the following query which displays a list of accounts with a certain margin level:
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
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?

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?
This can be done in several ways, but a scan of 22500 records taking 10" means either a hardware issue, or a very inefficient JOIN.
The most likely cause of the latter is a missing index or a misconfigured index, and to investigate this, you need to issue an EXPLAIN:
EXPLAIN SELECT ...
Totally shooting in the dark, judging from the selected columns being used, I'd try with
CREATE INDEX test_index ON crm_margincall(name, crm_account_id, MarginCallLevel, id)
Other improvements might be possible, but you'd need to prepare a sample structure with some fake data in a SQLfiddle to really allow debugging.

Answer 2

Try something like this:
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
INNER JOIN
(
SELECT
x.crm_account_id
FROM
crm_margincall x
WHERE
x.name = 'LevelDrop'
AND
x.MarginCallLevel < 100
AND
x.id > crm_margincall.id
) tt ON crm_margincall.crm_account_id = tt.crm_account_id
WHERE
crm_margincall.name = 'MarginCall'
AND
crm_margincall.MarginCallLevel >= 100
ORDER BY
id
DESC