Mybatis-Plus支持的聚合函数及其按日期查询功能

     //总收益
     		Order order =new Order();
        QueryWrapper<Order> queryWrapper = new QueryWrapper<Order>();
        queryWrapper.select("sum(price) as sumAll");     
        Order ord= orderService.getOne(queryWrapper);
        //注意，空指针问题
         if (ord== null){
            order.setSumAll(Double.valueOf(0)) ;
        }else{
    			 order.setSumAll(ord.getSumAll());
        }
       
    
    
    AI写代码java
    

    SELECT sum(price) a