i有一个带有名为reporttypeid的列的表。我想选择reportTypeid = 1的行,但是如果为此不存在行,那么我想要reportTypeid = 2。我想编写一个看起来像这样的查询:
SELECT CASE
WHEN EXISTS (SELECT PerformanceReport FROM ReportData
WHERE (ReportId = 79 and ReportTypeId = 1))
THEN (select * from ReferenceData
where ReportTypeId = 1)
ELSE (select * from ReferenceData
where ReportTypeId = 2)
END
但是,由于我试图返回多个列,所以它不起作用。有没有办法创建一个基于数据是否存在的陈述的查询?
如果可以订购 RecordTypeId
,则可以使用以下
SELECT PerformanceReport
FROM ReferenceData
WHERE ReportTypeId = (
SELECT MIN(ReportTypeId)
FROM ReportData
WHERE ReportTypeId IN (1, 2)
AND ReportId = 79
)
**按顺序,我的意思是MIN
聚合功能将返回预期的结果。但是,对于整数来说,这是有道理的,如果您的报告类型ID是文本UUID,则MIN
仍然可以正常工作,但不会给您预期的结果,因为它将按词汇顺序返回最小ID。
您可以使用以下解决方案:
SELECT *
FROM ReferenceData
WHERE (
ReportTypeId = 1
AND EXISTS (SELECT * FROM ReportData WHERE ReportTypeId = 1 AND ReportId = 79)
) OR (
ReportTypeId = 2
AND NOT EXISTS (SELECT * FROM ReportData WHERE ReportTypeId = 1 AND ReportId = 79)
)
您可以使用JOIN
:
SELECT ReferenceData.*
FROM ReferenceData JOIN (
SELECT EXISTS (SELECT * FROM ReportData WHERE ReportTypeId = 1 AND ReportId = 79) AS state
) isAvailable
WHERE (
ReportTypeId = 1 AND isAvailable.state = 1
) OR (
ReportTypeId = 2 AND isAvailable.state = 0
)
您可以使用JOIN
添加多个检查:
SELECT ReferenceData.*
FROM ReferenceData JOIN (
SELECT EXISTS (SELECT * FROM ReportData WHERE ReportTypeId = 1 AND ReportId = 79) AS state
) avail1 JOIN (
SELECT EXISTS (SELECT * FROM ReportData WHERE ReportTypeId = 2 AND ReportId = 79) AS state
) avail2 JOIN (
SELECT EXISTS (SELECT * FROM ReportData WHERE ReportTypeId = 3 AND ReportId = 79) AS state
) avail3
WHERE (
ReportTypeId = 1 AND avail1.state = 1
) OR (
ReportTypeId = 2 AND avail1.state = 0 AND avail2.state = 1
) OR (
ReportTypeId = 3 AND avail1.state = 0 AND avail2.state = 0 AND avail3.state = 1
) OR (
ReportTypeId = 4 AND avail1.state = 0 AND avail2.state = 0 AND avail3.state = 0
)
dbfiddle.uk上的演示
您似乎想要:
SELECT refd.*
FROM ReferenceData refd
WHERE (refd.ReportType = 1 AND
EXISTS (SELECT 1
FROM ReportData repd
WHERE repd.ReportId IN (1, 79)
)
) OR
(refd.ReportType = 2 AND
EXISTS (SELECT 1
FROM ReportData repd
WHERE repd.ReportId NOT IN (1, 79)
)
)