How to find orphaned records that point to different tables (paramerization required)?

Question

Table ( A ) has a 1-1 relation with many tables ( B, C, D, ... ) and is defined by two columns:

• ObjectType(nvarchar(100)) // name of the other table
• _Guid(uniqueidentifier) // record ID in the other table

Additionally, all tables contain an IsDeleted(bit) column.

The question is:

How to list all the records from (A) that point to non-existing record in B, C, D, (...) OR to the record that has IsDeleted = 1 set?

The following will not work because ObjectType must be a parameter:

SELECT ObjectType, _Guid FROM A
where 
    NOT EXISTS (
        select * from ObjectType where oid = _Guid
    )

The following will also not work:

SELECT ObjectType, _Guid FROM A
where 
    NOT EXISTS (
        exec('select * from '+ObjectType+' where oid =''' + _Guid + '''')
    )

What am I missing?

Answer 1

This terrible SQL below seems to work:

DECLARE @A_tmpTable TABLE (
    idx smallint Primary Key IDENTITY(1,1)
    , ObjectType nvarchar(200)
    , _Guid nvarchar(100)
    , Oid nvarchar(100)
)
DECLARE @orphanedA_tmpTable TABLE (
    Oid nvarchar(100)
)
DECLARE @_objectType nvarchar(200)
DECLARE @_Guid nvarchar(100)
DECLARE @_oid nvarchar(100)
DECLARE @i int, @numrows int  
DECLARE @found bit

-- populate temp table
INSERT @A_tmpTable SELECT ObjectType, _Guid, Oid FROM A WHERE IsDeleted = 0
--SELECT * FROM @A_tmpTable

-- foreach the @A_tmpTable
SET @i = 1;
SET @numrows = (SELECT COUNT(*) FROM @A_tmpTable)
--SELECT @i, @numrows 
IF @numrows > 0
    WHILE (@i <= @numrows)
    BEGIN
        SET @ObjectType = (SELECT TOP 1 ObjectType FROM @A_tmpTable WHERE idx = @i);
        SET @_Guid = (SELECT TOP 1 _Guid FROM @A_tmpTable WHERE idx = @i);
        SET @_oid = (SELECT TOP 1 Oid FROM @A_tmpTable WHERE idx = @i);

        DECLARE @SQL nvarchar(max) = 'IF EXISTS (SELECT * FROM '+@ObjectType+' WHERE OID =''' + @_Guid + ''' AND IsDeleted = 0) 
                SET @found = 1;
            ELSE
                SET @found = 0;
            ';
        -- check if table record exists and save the result in the @found variable
        exec sp_executesql @SQL, N'@found bit out', @found out

        IF @found = 0
            INSERT INTO @orphanedA_tmpTable (Oid) VALUES (@_oid);


        SET @i = @i + 1
    END

SELECT * FROM A WHERE Oid IN (SELECT Oid FROM @orphanedA_tmpTable)

Answer 2

Queries must have statically known structure to be optimized and executed. You can't use dynamic table names.

Join all possible tables.

SELECT *
FROM A
LEFT JOIN B ON ...
LEFT JOIN C ON ...
LEFT JOIN D ON ...
WHERE
 (B.IsDeleted IS NULL AND C.IsDeleted IS NULL AND D.IsDeleted IS NULL)
 OR (B.IsDeleted = 1 OR C.IsDeleted = 1 OR D.IsDeleted = 1)

I think I didn't get the condition exactly right because we need to match on ObjectType as well. I'll leave that for you to fix. The important idea is to join all possible tables, though.