varm=cn.QueryFirstOrDefault<dc_platform_balance>($"select * from dc_platform_balance where platformcode='{item.platformcode}' and currency='{item.currency}' and delstatus=0 and `day` <'{item.day.ToString("yyyy-MM-dd")}' order by day desc limit 1");
{
varm=cn.QueryFirstOrDefault<dc_platform_balance>($"select * from dc_platform_balance where platformcode='{item.platformcode}' and currency='{item.currency}' and delstatus=0 order by day desc limit 1");
varlist=cn.Query<dc_platform_balance>("select * from dc_platform_balance where delstatus=0 and day>='"+start.ToString("yyyy-MM-dd")+"' order by day ").AsList();