技術標籤：sql

1.三元運算子方式

//只統計數量,所以固定返回1和0;
var query = Db.Queryable<Orders,Service>((a, b) => new object[] {
                JoinType.Left,a.OrderID==b.OrderID
            });
 var infoDTO = query.Select((a, b) => new ServiceStatusCountDTO
             {
-                ConfirmCount = SqlFunc.AggregateSum(SqlFunc.IIF(a.ServiceStatus== Sea.Enum.OrderFlowStatus.dai_que_ren.GetStringValue(),1,0)),
-                HistoryCount = SqlFunc.AggregateSum(SqlFunc.IIF(a.ServiceStatus == Sea.Enum.OrderFlowStatus.yi_yan_shou.GetStringValue() && b.WarrantyExpiredDate < nowTime, 1, 0))
}).First();
 

2.if else方式

//此處示例沒有else判斷,省略了部分
var query = Db.Queryable<Orders,Service>((a, b) => new object[] {
                JoinType.Left,a.OrderID==b.OrderID
            });
var infoDTO = query.Select((a, b) => new ServiceStatusCountDTO
            {
                ConfirmCount = SqlFunc.AggregateSum(SqlFunc.IF(a.ServiceStatus== Sea.Enum.OrderFlowStatus.dai_que_ren.GetStringValue()).Return(1).End(0)),
                CompletedCount = SqlFunc.AggregateSum(SqlFunc.IF(a.ServiceStatus == Sea.Enum.OrderFlowStatus.yi_yan_shou.GetStringValue() && b.WarrantyExpiredDate >= nowTime).Return(1).End(0))
 }).First(); 
 

3.使用group by代替case when

4.group by和case when 在資料統計時效能上的區別