access 的多个left join 要加括号

string sql = "select a.orderId,a.UserName,b.CodeValue as Delivery ,a.DeliveryAddress,a.PhoneNum,c.CodeValue as Payment,d.CodeValue as OrderStatus,d.CodeValue as OrderStatusID,a.OrderTime,a.Merchant from (( m_Order a "; sql += " left join (

 string sql = "select  a.orderId,a.UserName,b.CodeValue as Delivery ,a.DeliveryAddress,a.PhoneNum,c.CodeValue as Payment,d.CodeValue as OrderStatus,d.CodeValue as OrderStatusID,a.OrderTime,a.Merchant from  (( m_Order a ";

            sql += " left join ( select CodeId,CodeValue from M_DefaultValue where TableId='Delivery') as b on a.Delivery =b.CodeId )";

            sql += " left join ( select CodeId,CodeValue from M_DefaultValue where TableId='Payment') as  c on a.Payment=c.CodeId )";

            sql += " left join ( select CodeId,CodeValue from M_DefaultValue where TableId='OrderStatu') as d on a.OrderStatus =d.CodeId ";

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