SQL語句連接語句

Question

我為創建SQL Server查詢而感到困惑。 我下面顯示了兩個表，它們之間存在一對多的關系。 我想進行所有活動並在if / where IsPrimary = true包含子圖片。

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'

活動 -ID-詳細信息

ActivityPicture -ImageLocation-說明-DateUploaded -IsPrimary -ActivityID

Answer 1

將您的INNER JOIN更改為LEFT OUTER JOIN 。 這將返回第一個表中的所有項目，無論它們是否在第二個表中都有子項目。

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'

這將返回所有活動對象，並在其中包含true的ActivityPicture.IsPrimaryPicture。