Question

I’m executing this query in a Sqlite database app, namely “Base.app” (can be found on the Mac App Store) and I get three result rows. I also get three rows if I execute the code below on iOS6. On iOS 5.1 however only one row is returned. No error.
I can reproduce the outcome of the one row on iOS6 and the DB app, if I remove the GROUP BY and the HAVING. But why would iOS5 ignore these?

SELECT COUNT(Sub.intItemID) AS intNumSubFolders, Items.*, Files.*
FROM Items
LEFT JOIN Items AS Sub ON Sub.intParentID = Items.intItemID AND Sub.intObjectType IN (2, 3, 6)
LEFT JOIN Files ON Files.intItemID = Items.intItemID 
WHERE Items.intParentID= 2905837
GROUP BY Items.intItemID HAVING Items.intItemVersion=MAX(Items.intItemVersion)

Here’s the code I use:

using ( SqliteCommand oCmd = new SqliteCommand ( "SELECT COUNT(Sub.intItemID) AS intNumSubFolders, Items.*, Files.*" +
                                                                " FROM Items" +
                                                                " LEFT JOIN Items AS Sub ON Sub.intParentID = Items.intItemID AND Sub.intObjectType IN (2, 3, 6)" +
                                                                " LEFT JOIN Files ON Files.intItemID = Items.intItemID " +
                                                                " WHERE Items.intParentID=@intItemID" +
                                                                " GROUP BY Items.intItemID HAVING Items.intItemVersion=MAX(Items.intItemVersion)", oConn ) )
                {
                    oCmd.Parameters.AddWithValue ( "@intItemID", iID );
                    using ( var oReader = oCmd.ExecuteReader (  ) )
                    {
                        while ( oReader.Read (  ) )
                        {
                            // getting here only once
                        }
                        oReader.Close ();
                    }
                }

Can somebody explain why this would happen? Confirmed on iOS5. In iOS6 it is working as expected.

Answer 1

We “fixed” it in the end by running an iOS version check. For 5.x we run two queries and combine the results in code. Not nice, but working.
After all, 90% of all users are on iOS 6.x anyway.