SQL语句连接语句

Question

I am stumped on creating a SQL server query. I have two tables shown below with a one to many relationship. I want to pull all activities and include the child pictures if/where IsPrimary = true .

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'

Activity -ID -Details

ActivityPicture -ImageLocation -Description -DateUploaded -IsPrimary -ActivityID

Answer 1

Change your INNER JOIN to a LEFT OUTER JOIN . This will return all items from the first table regardless of whether they have child items in the 2nd table.

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。