SQL - PostST - to relevant GL accounts (Sales, CoS, Stock)

select  S.code, S.Description_1,S.ServiceItem, WG.StGroup, WG.Description as WHGroupDesc
	, StockAccount.Master_Sub_Account + ' - ' + StockAccount.Description as StockAccount
	, CoSAccount.Master_Sub_Account + ' - ' + CoSAccount.Description as CosAccount
	,* 
	from PostST P
	left join StkItem S ON P.AccountLink = S.StockLink
	left join GrpTbl G ON S.ItemGroup = G.StGroup
	left join WhseStk WS ON P.WarehouseID = WS.IdWhseStk AND P.AccountLink = WS.WHStockLink
	left join GrpTbl WG on WS.WHStockGroup = WG.StGroup
	left join TrCodes ON P.TrCodeID = TrCodes.idTrCodes
	left join Accounts SalesAccount ON WG.SalesAccLink = SalesAccount.AccountLink
	left join Accounts CoSAccount ON CoSAccount.AccountLink =  CASE WHEN COALESCE(WG.COSAccLink,0) <> 0 THEN  WG.COSAccLink WHEN COALESCE(G.COSAccLink,0) <> 0 THEN G.COSAccLink ELSE TrCodes.Account2Link END
	left join Accounts StockAccount ON StockAccount.AccountLink = CASE WHEN COALESCE(WG.StockAccLink,0) <> 0 THEN  WG.StockAccLink WHEN COALESCE(G.StockAccLink,0) <> 0 THEN G.StockAccLink ELSE TrCodes.Account1Link END
	ORDER BY P.AutoIdx