mysql - 根据输入参数查询表

Question

我有一个要编写的查询的输入参数。基本上，ifmostRecentSnapshot == true那么我只想从进程运行中选择最新的记录(基本上where max(creationDate))和ifmostRecentSnapshot = = false 然后正常选择creationDate和其他列。

对我来说，在 from 子句中执行此 if 语句是有意义的，但我认为这是不可能的。通常我会使用 CTE，但 MySQL 中不存在这些。

实现这一目标的最佳方法是什么？

大概是这样的:

SELECT
CASE mostRecentSnapshot WHEN FALSE THEN 
(
processauditheader.creationDate as processCreationDate,
processauditheader.processName,
processauditheader.processType,
processauditheader.processHost,
processauditheader.processDatabase,
processauditheader.tableAudited,
processauditheader.processInvokedByName,
processauditheader.processInvokedByType,
processauditheader.processInvokedByDatabase,
processauditheader.processIntervalValue,
processauditheader.processIntervalField,
processauditheader.auditScenarios,
processaudititerationdetail.creationDate as iterationDate,
processaudititerationdetail.connectionId,
processaudititerationdetail.processDate,
processaudititerationdetail.tableRowCount,
processaudititerationdetail.tableRowCountLastDay,
processaudititerationdetail.previousProcessAuditIterationDetailID,
processauditmetricdetail.creationDate,
processauditmetricdetail.processAuditIterationDetailID,
processauditmetricdetail.auditMetric,
processauditmetricdetail.auditTotal,
processauditmetricdetail.auditExample
)
WHEN TRUE THEN 
(
((SELECT MAX(processaudititerationdetail.creationDate) as maxSnapshot,
processaudititerationdetail.id
from reporting_audit.processaudititerationdetail
group by processaudititerationdetail.creationDate) mostRecent

JOIN reporting_audit.processaudititerationdetail ON mostRecent.id = processaudititerationdetail.id)
)
END

FROM reporting_audit.processauditheader

JOIN processaudititerationdetail ON processaudititerationdetail.processAuditHeaderID = processauditheader.id
LEFT JOIN processauditmetricdetail ON processauditmetricdetail.processAuditIterationDetailID = processaudititerationdetail.id

Answer 1

查询只能返回一组固定的列。也许以下内容可以满足您的要求:

select paid.*
from reporting_audit.processaudititerationdetail paid
where (not v_mostRecentSnapshot) or
      paid.creation_date = (select max(paid2.creationDate from reporting_audit.processaudititerationdetail paid2);

它将选择表中的所有记录，或仅选择具有最新 creationDate 的记录。