两件事情：
SELECT Listing.Title
, Listing.MLS
, Pictures.PictureTH
, coalesce(Pictures.Picture, 'default.jpg') as Picture
, Listing.ID
FROM Listing LEFT OUTER JOIN Pictures ON Listing.ID = Pictures.ListingID
限制为一行：
SELECT Listing.Title
, Listing.MLS
, Pictures.PictureTH
, coalesce(Pictures.Picture, 'default.jpg') as Picture
, Listing.ID
FROM Listing
LEFT OUTER JOIN Pictures
ON Listing.ID = Pictures.ListingID
WHERE Pictures.ID is null
OR Pictures.ID = (SELECT MIN(ID)
FROM Pictures
WHERE (ListingID = Listing.ID)))
602392714
清零编程群