sqlserver sql语句易出错的地方

sqlserver数据库
1、update语句用别名：
得要这么用例如：
update bmd
set bmd.measure_money = bmd.measure_amount * (
select sb.unit_price
from sec_bill sb
where sb.sec_bill_id = bmd.sec_bill_id)
from bill_measure_detail bmd
where bill_measure_id IN (
select distinct bill_measure_id
from bill_measure
where project_id = @projectId
and section_id = @sectionId
and (measure_date >= @startDate and
              measure_date <= @endDate))

2、insert语句用group by:
insert into report_bill_num_vary
    (before_vary_num,before_vary_money,
     current_vary_num,current_vary_money
     sec_bill_id,vary_type_id,vary_no)
select before_vary_num,before_vary_price*before_vary_num,
    after_vary_num-before_vary_num,sum(vary_money)
    sec_bill_id,vary_type_id
from vary_detail
where vary_id = 11
group by before_vary_num,before_vary_price*before_vary_num,
    after_vary_num-before_vary_num,sec_bill_id,vary_type_id
select子句后面的所有字段，除了使用聚合函数的，都必须出现在group by子句后面

3、where和having区别
where是过滤分组前的数据，having是过滤分组后的数据(用到having，肯定用到group by)