This should get you started.
Select Top 1000000 tblAssets.AssetID,
tblAssets.AssetName,
tblADComputers.Description
From tblAssets
Inner Join tblAssetCustom On tblAssetCustom.AssetID = tblAssets.AssetID
Inner Join tblADComputers On tblADComputers.AssetID = tblAssets.AssetID
Where tblAssetCustom.State = 1
Order By tblAssets.AssetName