有人请解释父查询和子查询之间的区别吗?我怎么理解?
e.g:
SELECT
ra.ID id,
ra.ACCOUNT_ID accountId,
ef.REAL_NAME realName,
a.MOBILE mobile,
sps.`NAME` siteName,
ef.CREATE_TIME createTime,
a.`STATUS` status,
ra.`STATUS` siteStatus,
(
SELECT
aif.APPROVER_NAME
FROM
audit_info aif
WHERE
aif.TARGET_ID = a.ID AND af.AUDIT_TYPE=2
AND aif.CREATE_TIME = (
SELECT
MAX(af.CREATE_TIME)
FROM
audit_info af
WHERE
af.TARGET_ID = a.ID AND af.AUDIT_TYPE=2
)
) AS approverName
FROM
account a
INNER JOIN site_relation_account ra ON ra.ACCOUNT_ID = a.ID
INNER JOIN account_ext ef ON ra.ACCOUNT_ID = ef.ACCOUNT_ID
INNER JOIN service_provider_site sps ON sps.ID = ra.SITE_ID
LEFT JOIN audit_info af ON af.TARGET_ID = ef.ACCOUNT_ID
WHERE ra.ACCOUNT_TYPE = 2