SQL语句连接语句

Question

我为创建SQL Server查询而感到困惑。 我下面显示了两个表，它们之间存在一对多的关系。 我想进行所有活动并在if / where IsPrimary = true包含子图片。

SELECT dbo.Activity.ID, dbo.Activity.Details, dbo.ActivityPicture.DateUploaded, dbo.ActivityPicture.IsPrimaryPicture, dbo.ActivityPicture.ImageData
FROM dbo.ReportTask 
INNER JOIN dbo.ActivityPicture ON dbo.Activity.ID = dbo.ActivityPicture .ActivityID AND dbo.ActivityPicture.IsPrimaryPicture = 'true'

活动 -ID-详细信息

ActivityPicture -ImageLocation-说明-DateUploaded -IsPrimary -ActivityID

Answer 1

将您的INNER JOIN更改为LEFT OUTER JOIN 。 这将返回第一个表中的所有项目，无论它们是否在第二个表中都有子项目。

Answer 2

SELECT dbo.Activity.ID, dbo.Activity.Details, dbo.ActivityPicture.DateUploaded, dbo.ActivityPicture.IsPrimaryPicture, dbo.ActivityPicture.ImageData FROM dbo.ReportTask LEFT JOIN dbo.ActivityPicture ON dbo.Activity.ID = dbo.ActivityPicture .ActivityID AND dbo.ActivityPicture.IsPrimaryPicture = 'true'

这将返回所有活动对象，并在其中包含true的ActivityPicture.IsPrimaryPicture。